Document And Entity Information (USD $) In Billions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Jan. 31, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Trading Symbol	SEIC
Entity Registrant Name	SEI INVESTMENTS CO
Entity Central Index Key	0000350894
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		176,591,930
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 3.2

Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current Assets:
Cash and cash equivalents	$ 420,986	$ 496,292
Restricted cash	6,000	4,000
Receivables from regulated investment companies	25,800	29,282
Receivables, net of allowance for doubtful accounts of $924 and $1,195 (Note 4)	142,109	136,490
Deferred income taxes, net	1,150	1,387
Securities owned	20,949	0
Other current assets	17,957	16,268
Total Current Assets	634,951	683,719
Property and Equipment, net of accumulated depreciation of $182,453 and $166,816 (Note 4)	129,548	140,568
Capitalized Software, net of accumulated amortization of $117,100 and $90,947	309,133	294,332
Investments Available for Sale (Note 6)	83,008	74,770
Trading Securities (Note 6)	56,325	104,594
Investment in Unconsolidated Affiliate (Note 2)	60,954	64,409
Other Assets, net	20,640	14,831
Total Assets	1,294,559	1,377,223
Current Liabilities:
Accounts payable	1,999	4,582
Accrued liabilities (Note 4)	147,044	121,410
Deferred revenue	2,030	1,608
Total Current Liabilities	151,073	127,600
Long-term Debt (Note 7)	0	95,000
Deferred Income Taxes	93,751	92,253
Other Long-term Liabilities (Note 12)	8,276	5,645
Total Liabilities	253,100	320,498
Commitments and Contingencies (Note 11)
SEI Investments Company shareholders' equity:
Series Preferred stock, $.05 par value, 50 shares authorized; no shares issued and outstanding	0	0
Common stock, $.01 par value, 750,000 shares authorized; 176,506 and 186,141 shares issued and outstanding	1,765	1,861
Capital in excess of par value	577,949	565,393
Retained earnings	443,702	471,159
Accumulated other comprehensive income, net	1,900	3,157
Total SEI Investments Shareholders' Equity	1,025,316	1,041,570
Noncontrolling interest	16,143	15,155
Total Equity	1,041,459	1,056,725
Total liabilities and partners' capital	$ 1,294,559	$ 1,377,223

Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Receivables, allowance for doubtful accounts	$ 924	$ 1,195
Property and Equipment, accumulated depreciation and amortization	182,453	166,816
Capitalized Software, accumulated amortization	$ 117,100	$ 90,947
Series Preferred stock, par value	$ 0.05	$ 0.05
Series Preferred stock, shares authorized	50,000	50,000
Series Preferred stock, shares issued	0	0
Preferred stock, share outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	176,506,000	186,141,000
Common stock, shares outstanding	176,506,000	186,141,000

Consolidated Statements Of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Asset management, administration and distribution fees	$ 669,788	$ 628,535	$ 773,186
Information processing and software servicing fees	222,417	231,529	231,807
Transaction-based and trade execution fees	37,522	40,771	55,555
Total revenues	929,727	900,835	1,060,548
Expenses:
Subadvisory, distribution and other asset management costs	103,134	101,722	94,449
Software royalties and other information processing costs	27,437	24,419	21,509
Brokerage commissions	27,022	28,882	41,146
Compensation, benefits and other personnel	289,445	269,165	274,675
Stock-based compensation	14,112	26,783	14,503
Consulting, outsourcing and professional fees	113,171	89,033	81,694
Data processing and computer related	47,003	41,064	45,403
Facilities, supplies and other costs	55,579	56,284	57,323
Amortization	27,288	24,048	44,608
Depreciation	21,471	21,902	21,531
Total expenses	725,662	683,302	696,841
Income from operations	204,065	217,533	363,707
Net gain (loss) from investments	3,360	48,533	(4,926)
Interest and dividend income	5,829	6,326	7,281
Interest expense	(585)	(1,478)	(3,744)
Other expense, net	0	(590)	0
Equity in earnings of unconsolidated affiliate	105,818	99,457	0
Net income before income taxes	318,487	369,781	362,318
Income taxes	111,837	136,461	89,886
Net income	206,650	233,320	272,432
Less: Net income attributable to the noncontrolling interest	(1,691)	(1,633)	(98,097)
Net income attributable to SEI Investments Company	$ 204,959	$ 231,687	$ 174,335
Basic earnings per common share	$ 1.12	$ 1.23	$ 0.91
Diluted earnings per common share	$ 1.11	$ 1.22	$ 0.91

Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Comprehensive Income [Abstract]
Net income	$ 206,650	$ 233,320	$ 272,432
Other comprehensive (loss) gain, net of tax:
Foreign currency translation adjustments	(3,195)	2,205	8,734
Unrealized holding gain on investments:
Unrealized holding gains during the period, net of income taxes of $(811), $(486) and $(1,065)	1,369	484	2,124
Less: reclassification adjustment for (gains) losses realized in net income, net of income taxes of $77, $56 and $(222)	(134)	(105)	360
Total other comprehensive (loss) gain, net of taxes	(1,960)	2,584	11,218
Comprehensive income	204,690	235,904	283,650
Less: Comprehensive income attributable to noncontrolling interest	(988)	(2,318)	(99,894)
Comprehensive income attributable to SEI Investments	$ 203,702	$ 233,586	$ 183,756

Consolidated Statements Of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Comprehensive Income [Abstract]
Unrealized holding gains during the period, income taxes	$ (811)	$ (486)	$ (1,065)
Reclassification adjustment for gains (losses) realized in net income, income taxes	$ 77	$ 56	$ (222)

- Definition

Tax effect on the reclassification adjustment for gains or losses realized upon the sale of securities during the period.

+ References+ Details

- Definition

Tax effect on gross appreciation or the gross loss in value of the total of unsold securities during the period being reported on.

+ References+ Details

Consolidated Statements Of Changes In Equity (USD $) In Thousands, except Share data	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	SEI Investments Company [Member]	Noncontrolling Interest [Member]	Total
Beginning balance at Dec. 31, 2008	$ 1,912	$ 485,721	$ 289,682	$ (8,163)
Beginning balance, shares at Dec. 31, 2008	191,195,000
Net income attributable to SEI Investments Company			174,335				174,335
Purchase and retirement of common stock	(32)	(6,970)	(47,112)				54,114
Purchase and retirement of common stock, shares	(3,198,000)						3,198,000
Issuance of common stock under the employee stock purchase plan	2	2,035
Issuance of common stock under the employee stock purchase plan, shares	156,000
Issuance of common stock upon exercise of stock options	20	21,607
Issuance of common stock upon exercise of stock options, shares	2,055,000
Stock-based compensation		13,962					14,503
Tax benefit on stock options exercised		5,725
Dividends declared			(32,422)
Other comprehensive (loss) income				9,421	11,218		11,218
Total SEI Investments Shareholders' Equity					909,723
Noncontrolling interest						121,895	121,895
Total Equity at Dec. 31, 2009	1,902	522,080	384,483	1,258			1,031,618
Ending balance, shares at Dec. 31, 2009	190,208,000
Net income attributable to SEI Investments Company			231,687				231,687
Purchase and retirement of common stock	(58)	(13,426)	(107,498)				120,982
Purchase and retirement of common stock, shares	(5,814,000)						5,814,000
Issuance of common stock under the employee stock purchase plan	1	1,902
Issuance of common stock under the employee stock purchase plan, shares	114,000
Issuance of common stock upon exercise of stock options	16	26,177
Issuance of common stock upon exercise of stock options, shares	1,633,000
Stock-based compensation		26,783					26,783
Tax benefit on stock options exercised		1,877
Dividends declared			(37,513)
Other comprehensive (loss) income				1,899	2,584		2,584
Total SEI Investments Shareholders' Equity					1,041,570		1,041,570
Noncontrolling interest						15,155	15,155
Total Equity at Dec. 31, 2010	1,861	565,393	471,159	3,157			1,056,725
Ending balance, shares at Dec. 31, 2010	186,141,000						186,141,000
Net income attributable to SEI Investments Company			204,959				204,959
Purchase and retirement of common stock	(111)	(27,196)	(183,858)				211,165
Purchase and retirement of common stock, shares	(11,109,000)						11,109,000
Issuance of common stock under the employee stock purchase plan	1	1,892
Issuance of common stock under the employee stock purchase plan, shares	110,000
Issuance of common stock upon exercise of stock options	14	22,314
Issuance of common stock upon exercise of stock options, shares	1,364,000
Stock-based compensation		14,112					14,112
Tax benefit on stock options exercised		1,434
Dividends declared			(48,558)
Other comprehensive (loss) income				(1,257)	(1,960)		(1,960)
Total SEI Investments Shareholders' Equity					1,025,316		1,025,316
Noncontrolling interest						16,143	16,143
Total Equity at Dec. 31, 2011	$ 1,765	$ 577,949	$ 443,702	$ 1,900			$ 1,041,459
Ending balance, shares at Dec. 31, 2011	176,506,000						176,506,000

Consolidated Statements Of Cash Flows (USD $)
In Thousands, unless otherwise specified

12 Months Ended

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Cash flows from operating activities:

Net income

$ 206,650

$ 233,320

$ 272,432

Adjustments to reconcile net income to net cash provided by operating activities:

Amortization

27,288

24,048

44,608

Depreciation

21,471

21,902

21,531

Equity in earnings of unconsolidated affiliate

(105,818)

(99,457)

Cash received from unconsolidated affiliate

109,273

72,060

Payments to partners of LSV

(87,337)

Stock-based compensation

14,112

26,783

14,503

Provision for losses on receivables

(271)

(1,004)

692

Deferred income tax expense

1,001

6,461

67,265

Net realized (gains) losses from investments

(3,360)

(48,533)

178,007

Other-than-temporary declines in market value

901

Change in other long-term liabilities

2,631

(81)

1,659

Other

(2,833)

2,473

3,508

Decrease (increase) in:

Restricted cash for broker-dealer operations

16,000

Receivables from regulated investment companies

3,482

(1,148)

230

Receivables

(11,474)

(11,032)

(3,885)

Other current assets

(1,689)

(1,101)

197

Increase (decrease) in:

Accounts payable

(2,583)

1,734

(9,457)

Capital Support Agreements

(173,983)

Payable to regulated investment companies

(97)

Accrued liabilities

(1,340)

(13,847)

15,367

Deferred revenue

422

748

(670)

Total adjustments

50,312

(3,994)

73,039

Net cash provided by operating activities

256,962

229,326

345,471

Cash flows from investing activities:

Additions to restricted cash

(2,000)

(6,000)

Additions to property and equipment

(12,271)

(13,611)

(19,272)

Additions to capitalized software

(40,954)

(38,729)

(43,944)

Purchases of marketable securities

(73,960)

(39,085)

(322,528)

Prepayments and maturities of marketable securities

61,582

58,174

32,002

Sales of marketable securities

38,247

28,859

20,830

Purchases of other investments

(7,500)

Sales of other investments

4,906

LSV and LSV Employee Group cash balances, net

^[1]

(37,083)

^[1]

Net cash used in investing activities

(31,950)

(41,475)

(338,912)

Cash flows from financing activities:

Proceeds from borrowings on long-term debt

254,000

Payments on long-term debt

(95,000)

(138,000)

(31,980)

Purchase and retirement of common stock

(208,932)

(119,775)

(53,136)

Proceeds from issuance of common stock

24,221

28,096

23,664

Tax benefit on stock options exercised

1,434

1,877

5,725

Payment of dividends

(22,041)

(54,634)

(30,598)

Net cash (used in) provided by financing activities

(300,318)

(282,436)

167,675

Net (decrease) increase in cash and cash equivalents

(75,306)

(94,585)

174,234

Cash and cash equivalents, beginning of year

496,292

590,877

416,643

Cash and cash equivalents, end of year

420,986

496,292

590,877

Interest paid

559

1,488

4,676

Income taxes paid

116,483

145,553

9,052

Non-cash financing activities

Dividends declared but not paid

$ 26,518

$ 0

$ 17,121

[1]	Cash balances, net of the partnership distribution payment received in January 2010, of LSV and LSV Employee Group at December 31, 2009 removed due to the deconsolidation of the accounts and operations of LSV and LSV Employee Group in January 2010 (See Note 2).

Summary Of Significant Accounting Policies

12 Months Ended

Dec. 31, 2011

Summary Of Significant Accounting Policies [Abstract]

Summary Of Significant Accounting Policies

Note 1 – Summary of Significant Accounting Policies:

Nature of Operations

SEI Investments Company (the Company), a Pennsylvania corporation, provides investment processing, investment management, and investment operations solutions to corporations, financial institutions, financial advisors, and ultra-high-net-worth families in the United States, Canada, the United Kingdom, continental Europe, and other various locations throughout the world. Investment processing solutions consist of application and business process outsourcing services, professional services and transaction-based services. Revenues from investment processing solutions are recognized in Information processing and software servicing fees on the accompanying Consolidated Statements of Operations, except for fees earned associated with trade execution services.

Investment management programs consist of mutual funds, alternative investments and separate accounts. These include a series of money market, equity, fixed-income and alternative investment portfolios, primarily in the form of registered investment companies. The Company serves as the administrator and investment advisor for many of these products. Revenues from investment management programs are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations.

Investment operations solutions offer investment managers support for traditional investment products such as mutual funds, collective investment trusts, exchange-traded funds, and institutional and separate accounts, by providing outsourcing services including fund and investment accounting, administration, reconciliation, investor servicing and client reporting. These solutions also provide support to managers focused on alternative investments who manage hedge funds, funds of hedge funds, private equity funds and real estate funds, across registered, partnership and separate account structures domiciled in the United States and overseas. Revenues from investment operations solutions are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations.

Principles of Consolidation

The Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries and entities in which it holds a controlling financial interest. The Company determines whether it has a controlling financial interest either by its decision-making ability through voting interests or by the extent of the Company's participation in the economic risks and rewards of the entity through variable interests. The Company accounts for noncontrolling interests in consolidated entities for which the Company's controlling financial interest is less than 100 percent. The Company's principal subsidiaries are SEI Investments Distribution Co. (SIDCO), SEI Investments Management Corporation (SIMC), SEI Private Trust Company (SPTC), SEI Trust Company (STC), SEI Global Services, Inc. (SGSI) and SEI Investments (Europe) Limited (SIEL). All intercompany accounts and transactions have been eliminated.

In January 2010, new accounting guidance pertaining to the consolidation of VIEs became effective. Under the new guidance, the Company was not considered the primary beneficiary of LSV Employee Group (See Note 2). The Company, therefore, discontinued consolidating the accounts and operations of LSV Asset Management (LSV) and LSV Employee Group in its financial statements. The Company accounts for its interest in LSV using the equity method because of its less than 50 percent ownership. The Company's interest in the net assets of LSV is reflected in Investment in unconsolidated affiliate on the accompanying Consolidated Balance Sheet and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliate on the accompanying Consolidated Statement of Operations. The deconsolidation of LSV had no effect on Net income attributable to SEI. Prior period financial statements are not reclassified for the new accounting guidance.

Noncontrolling interest on the accompanying Consolidated Balance Sheets includes the interest of other shareholders in a joint venture of the Company in an asset management firm located in South Korea.

Variable Interest Entities

The Company has involvement with various variable interest entities (VIE or VIEs). These VIEs consist of LSV Employee Group and investment products established for clients created in the form of various types of legal entity structures. In June 2009, the Financial Accounting Standards Board (FASB) issued guidance related to the consolidation of VIEs. This guidance changed how a company determines when an entity that is insufficiently capitalized or is not controlled through voting common stock should be consolidated. The determination of whether a company is required to consolidate an entity is based on, among other things, an entity's purpose and design, a company's ability to direct the activities of the entity that most significantly impact the entity's economic performance, and whether a company is obligated to absorb losses or receive benefits that could be potentially significant to the entity. The guidance requires ongoing reassessments of whether an enterprise is the primary beneficiary of a VIE and requires disclosures about an enterprises involvement in VIEs.

Under the new guidance, LSV Employee Group remains a VIE. However, the Company is not considered the primary beneficiary because it does not have the power to direct the activities that most significantly impact the economic performance of LSV Employee Group either directly or through any financial responsibility from the Guaranty Agreement. As of January 1, 2010, the Company discontinued consolidating the accounts of LSV Employee Group. The Company does not have any direct equity interest in LSV Employee Group.

In January 2010, the FASB deferred the new guidance for certain types of investment entities. The deferral allows asset managers that have no obligation to fund potentially significant losses of an investment entity to continue to apply the previous guidance to investment entities that have attributes of entities defined in the "Investment Company Guide." The deferral applies to many mutual funds, hedge funds, private equity funds, venture capital and certain other types of entities. Also, money market funds subject to rule 2a-7 of the Investment Company Act of 1940 qualify for deferral. However, the deferral does not apply to the new disclosure requirements. All of the Company's investment products where the Company is the sponsor and/or investment manager that are VIEs qualify for the deferral; therefore, the Company will continue to apply the previous guidance for the consolidation of VIEs (See Note 3).

Management's Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Revenue Recognition

The Company's principal sources of revenues are: (1) asset management, administration and distribution fees earned based upon a contractual percentage of net assets under management or administration; (2) information processing and software servicing fees that are either recurring and primarily earned based upon the number of trust accounts being serviced or non-recurring and based upon project-oriented contractual agreements related to client implementations; and (3) transaction-based fees for providing trade-execution services. The majority of the Company's revenues are based on contractual arrangements. Revenues are recognized in the periods in which the related services are performed provided that persuasive evidence of an agreement exists, the fee is fixed or determinable, and collectibility is reasonably assured. Cash received by the Company in advance of the performance of services is deferred and recognized as revenue when earned. Reimbursements received for out-of-pocket expenses incurred are recorded as revenue. Certain portions of the Company's revenues require management's consideration of the nature of the client relationship in determining whether to recognize as revenue the gross amount billed or net amount retained after payments are made to suppliers for certain services related to the product or service offering.

Cash and Cash Equivalents

The Company considers investment instruments purchased with an original maturity of three months or less to be cash equivalents. Cash and cash equivalents include $281,760 and $383,946 at December 31, 2011 and 2010, respectively, primarily invested in SEI-sponsored open-ended money market mutual funds.

Restricted Cash

Restricted cash includes $5,000 and $3,000 at December 31, 2011 and 2010, respectively, segregated for regulatory purposes related to trade-execution services conducted by SIEL. Restricted cash also includes $1,000 at December 31, 2011 and 2010 segregated in special reserve accounts for the benefit of SIDCO customers in accordance with certain rules established by the Securities and Exchange Commission for broker-dealers.

Allowances for Doubtful Accounts

The Company provides an allowance for doubtful accounts equal to the estimated uncollectible amounts. The Company's estimate is based on historical collection experience and a review of the current status of trade accounts receivable.

Concentration of Credit Risk

Financial instruments which potentially expose the Company to concentrations of credit risk consist primarily of cash equivalents and trade receivables. Cash equivalents are principally invested in short-term money market funds or placed with major banks and high-credit qualified financial institutions. Cash deposits maintained with institutions are in excess of federally insured limits. Concentrations of credit risk with respect to our receivables are limited due to the large number of clients and their dispersion across geographic areas. No single group or customer represents greater than ten percent of total accounts receivable.

Property and Equipment

Property and Equipment are recorded at cost. Expenditures for major additions and improvements are capitalized and minor replacements, maintenance, and repairs are charged to expense as incurred. Construction in progress includes the cost of construction and other direct costs attributable to the construction. When property and equipment are retired or disposed of, the related cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the results of operations for the respective period. Depreciation is provided over the estimated useful lives using the straight line method for financial statement purposes. No provision for depreciation is made for construction in progress until such time as the relevant assets are completed and put into service. The Company uses other depreciation methods, generally accelerated, for tax purposes where appropriate. Buildings and building improvements are depreciated over 25 to 39 years. Equipment, purchased software and furniture and fixtures have useful lives ranging from three to five years. Amortization of leasehold improvements is computed using the straight line method over the shorter of the remaining lease term or the estimated useful lives of the improvements

Marketable Securities

The classification of investments in marketable securities is determined at the time of purchase and reevaluated at each balance sheet date. Debt and equity securities classified as available-for-sale are reported at fair value as determined by the most recently traded price of each security at the balance sheet date. Unrealized gains and losses, net of income taxes, are reported as a separate component of comprehensive income. SIDCO, the Company's broker-dealer subsidiary, reports changes in fair value of marketable securities through current period earnings due to specialized accounting practices related to investments by broker-dealers. The Company records all of its trading securities on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these securities are recognized in current period earnings. The specific identification method is used to compute the realized gains and losses on all of the Company's marketable securities (See Note 6).

The Company evaluates the realizable value of its marketable securities on a quarterly basis. In the event that the carrying value of an investment exceeds its fair value and the decline in value is determined to be other-than-temporary, an impairment charge is recorded and a new cost basis for the investment is established. Some of the factors considered in determining other-than-temporary impairment for equity securities include, but are not limited to, significant or prolonged declines in the fair value of the investments, the Company's ability and intent to retain the investment for a period sufficient to allow the value to recover, and the financial condition of the investment. Some of the factors considered in determining other-than-temporary impairment for debt securities include, but are not limited to, the intent of management to sell the security, the likelihood that the Company will be required to sell the security before recovering its cost, and management's expectation to recover the entire amortized cost basis of the security even if there is no intent to sell the security.

Fair Value of Financial Instruments

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The fair value hierarchy describes three levels of inputs that may be used by the Company to measure fair value:

Level 1 – Quoted prices in active markets for identical assets or liabilities without adjustment. The Company's Level 1 assets primarily include investments in mutual funds sponsored by SEI and LSV that are quoted daily.

Level 2 – Observable inputs other than Level 1 prices, such as quoted prices for similar assets, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The Company's Level 2 assets primarily include securities issued by the Government National Mortgage Association (GNMA) and other U.S. government agency securities that are single issuer pools that are valued based on current market data for the specific issue owned or pools of similar securities. The Company uses a pricing vendor to value its GNMA securities. The pricing vendor uses a pricing model with inputs that are observable in the market or can be derived principally from or corroborated by observable market data for similar pools of GNMA securities.

Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment by management. The Company's Level 3 financial assets primarily include structured investment vehicles (SIV) securities and any change in fair value for these securities is recognized in the current period.

The fair value of an asset or liability may include inputs from more than one level in the fair value hierarchy. The lowest level of significant inputs used to value the asset or liability determines which level the asset or liability is classified in its entirety.

See Note 5 for information on related disclosures regarding fair value measurements

Capitalized Software

Costs incurred for the development of internal use software to be offered in a hosting arrangement is capitalized during the development stage of the software application. These costs include direct external and internal costs to design the software configuration and interfaces, coding, installation, and testing. Costs incurred during the preliminary and post-implementation stages of the software application are expensed as incurred. Costs associated with significant enhancements to a software application are capitalized while costs incurred to maintain existing software applications are expensed as incurred. The capitalization of software development costs requires considerable judgment by management with respect to certain external factors, including, but not limited to, technological and economic feasibility, and estimated economic life. Capitalized software development costs in 2011, 2010 and 2009 primarily relate to the further development of the Global Wealth Platform (GWP). The initial version of GWP was placed into service in July 2007. Further enhancements and upgrades will continue to occur through a series of releases. As of December 31, 2011, the net book value of GWP was $296,687, net of accumulated amortization of $87,762. Capitalized software development costs in-progress at December 31, 2011 associated with future releases to GWP were $11,552. The Company capitalized $40,954, $38,729, and $43,944 of software development costs during 2011, 2010, and 2009, respectively.

Amortization of capitalized software development costs begins when the product is ready for its intended use. Capitalized software development costs are amortized on a product-by-product basis using the straight-line method over the estimated economic life of the product or enhancement, which is primarily 3 to 15 years, with a weighted average remaining life of approximately 10.5 years. Amortization expense was $26,153, $23,053, and $35,894 in 2011, 2010, and 2009, respectively, and is included in Amortization expense on the accompanying Consolidated Statements of Operations. GWP has an estimated useful life of 15 years and a weighted average remaining life of 10.5 years. The Company abandoned certain components within GWP that were replaced in late 2009. The useful life of these components was shortened so that the remaining net book value of $15,502 was fully amortized commensurate with the new release. Amortization expense in 2009 on the Consolidated Statements of Operations includes $15,502 of accelerated amortization for these components.

The Company evaluates the carrying value of capitalized software development costs when circumstances indicate the carrying value may not be recoverable. The review of capitalized software development costs for impairment requires significant assumptions about operating strategies, underlying technologies utilized, and external market factors. External market factors include, but are not limited to, expected levels of competition, barriers to entry by potential competitors, stability in the target market and governmental regulations. In 2011 and 2010, the Company determined that no events or change in circumstances had occurred that would indicate that capitalized software development costs were impaired. Therefore, the Company did not recognize any impairment charges for any of its capitalized software development costs in 2011 or 2010.

Income Taxes

The Company applies the asset and liability approach to account for income taxes whereby deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The components of the deferred tax assets and liabilities are individually classified as current and non-current based on their characteristics.

Foreign Currency Translation

The assets and liabilities and results of operations of the Company's foreign subsidiaries are measured using the foreign subsidiary's local currency as the functional currency. Assets and liabilities have been translated into U.S. dollars using the rates of exchange at the balance sheet dates. The results of operations have been translated into U.S. dollars at average exchange rates prevailing during the period. The resulting translation gain and loss adjustments are recorded as a separate component of comprehensive income.

Transaction gains and losses that arise from exchange rate fluctuations are included in the results of operations in the periods in which they occur, and are immaterial for each of the years in the three year period ended December 31, 2011.

Earnings Per Common Share

Basic earnings per common share is computed by dividing net income attributable to SEI Investments common shareholders by the weighted average number of common shares outstanding during the period. Diluted earnings per common share is computed by dividing net income attributable to SEI Investments common shareholders by the combination of the weighted average number of common shares outstanding and the dilutive potential common shares, such as stock options, outstanding during the period. The calculations of basic and diluted earnings per share for 2011, 2010, and 2009 are:


	For the Year ended December 31, 2011
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	204,959		182,547	$	1.12
Dilutive effect of stock options		0		1,580


Diluted earnings per common share	$	204,959		184,127	$	1.11


	For the Year ended December 31, 2010
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	231,687		188,468	$	1.23
Dilutive effect of stock options		0		1,853


Diluted earnings per common share	$	231,687		190,321	$	1.22


	For the Year ended December 31, 2009
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	174,335		190,821	$	0.91
Dilutive effect of stock options		0		962


Diluted earnings per common share	$	174,335		191,783	$	0.91

Employee stock options to purchase approximately 15,914,000, 13,181,000, and 22,997,000 shares of common stock, with an average exercise price per share of $23.07, $23.79, and $21.47, were outstanding during 2011, 2010, and 2009, respectively, but not included in the computation of diluted earnings per common share because the option's exercise price was greater than the average market price of the Company's common stock and the effect on diluted earnings per common share would have been anti-dilutive (See Note 8).

Stock-Based Compensation

Stock-based compensation cost is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which is the vesting period. The Company uses historical data to estimate pre-vesting forfeitures and record stock-based compensation expense only for those awards that are expected to vest. The amount of stock-based compensation expense that is recognized in a given period is dependent upon management's estimate of when the vesting targets are expected to be achieved. If this estimate proves to be inaccurate, the remaining amount of stock-based compensation expense could be accelerated, spread out over a longer period, or reversed (See Note 8).

New Accounting Pronouncements

In May 2011, the Financial Accounting Standards Board (FASB) issued a final Accounting Standards Update which represents the converged guidance of the FASB and the International Accounting Standards Board on fair value measurement. The guidance clarifies how a principal market is determined, addresses the fair value measurement of instruments with offsetting market or counterparty credit risks, addresses the concept of valuation premise and highest and best use, extends the prohibition on blockage factors to all three levels of the fair value hierarchy and requires additional disclosures. The guidance is effective for interim and annual periods beginning after December 15, 2011 and is applied prospectively. The Company does not expect the adoption of the guidance to have a significant impact on its consolidated financial statements.

In June 2011, the FASB issued a final Accounting Standards Update to amend the presentation of comprehensive income in financial statements. This new guidance allows companies the option to present other comprehensive income in either a single continuous statement or in two separate but consecutive statements. Under both alternatives, companies will be required to present each component of net income and comprehensive income. The guidance is effective for interim and annual periods beginning after December 15, 2011 and is applied retrospectively. The Company does not expect the adoption of the guidance to have any impact on its consolidated financial statements.

Reclassifications

Certain prior year amounts have been reclassified to conform to current year presentation.

- Definition

The entire disclosure for all significant accounting policies of the reporting entity.

+ References+ Details

Investment In Unconsolidated Affiliate

12 Months Ended

Dec. 31, 2011

Investment In Unconsolidated Affiliate [Abstract]

Investment In Unconsolidated Affiliate

Note 2 – Investment in Unconsolidated Affiliate

The Company has an investment in LSV, a general partnership and registered investment advisor that provides investment advisory services to institutions, including pension plans and investment companies. LSV is currently an investment sub-advisor for a number of SEI-sponsored mutual funds. As of December 31, 2011, the Company's total partnership interest in LSV was approximately 41 percent.

LSV Employee Group is owned by several current employees of LSV and was formed for the sole purpose of owning a partnership interest in LSV. The Company does not own any interest in LSV Employee Group. In 2006, LSV Employee Group purchased an eight percent interest in LSV from two existing partners. LSV Employee Group obtained financing in the form of a term loan pursuant to the terms of a Credit Agreement to purchase the eight percent interest in LSV. The Company agreed to provide a Guaranty Agreement to the lenders of all obligations of LSV Employee Group under the Credit Agreement. The lenders have the right to seek payment from the Company of all obligations of LSV Employee Group under the Credit Agreement in the event of default. The Company's direct interest in LSV was unchanged as a result of this transaction.

As a result of providing the Guaranty Agreement, LSV Employee Group became a VIE and the Company was considered the primary beneficiary. Also, given the Company's direct ownership of 43 percent in LSV at the time of this transaction in 2006 and its controlling interest in LSV Employee Group through the Guaranty Agreement, the Company was required to consolidate the assets, liabilities and operations of LSV and LSV Employee Group. The partnership interest of the other existing partners of LSV was included in Noncontrolling interest.

In January 2010, new accounting guidance pertaining to the consolidation of VIEs became effective. Under the new guidance, the Company was not considered the primary beneficiary of LSV Employee Group. The Company, therefore, discontinued consolidating the accounts and operations of LSV and LSV Employee Group in its financial statements. The Company accounts for its interest in LSV using the equity method because of its less than 50 percent ownership. The Company's interest in the net assets of LSV is reflected in Investment in unconsolidated affiliate on the accompanying Consolidated Balance Sheet and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliate on the accompanying Consolidated Statement of Operations. The deconsolidation of LSV had no effect on Net income attributable to SEI. Prior period financial statements are not reclassified for the new accounting guidance.

LSV Asset Management

At December 31, 2011, the Company's total investment in LSV was $60,954. The investment in LSV exceeded the underlying equity in the net assets of LSV by $3,717, of which $3,062 is considered goodwill embedded in the investment. The Company receives partnership distributions from LSV on a quarterly basis. The Company received partnership distribution payments from LSV for $109,273, $93,302 and $73,518 in 2011, 2010 and 2009, respectively. The partnership distribution payment of $21,242 received in January 2010 is reflected in LSV and LSV Employee Group cash balances, net on the accompanying Consolidated Statement of Cash Flows.

These tables contain condensed financial information of LSV:


Condensed Statement of Operations Year ended December 31,	2011		2010

Revenues	$	296,397	$	273,381

Net income	$	257,519	$	239,981


Condensed Balance Sheet December 31,	2011		2010

Cash and cash equivalents	$	60,728	$	64,464
Accounts receivable, net of allowance for doubtful accounts of $804 and $369		75,269		75,056
Prepaid expenses and other current assets		604		848
Non-current assets		3,880		4,159


Total assets	$	140,481	$	144,527

Current liabilities	$	13,933	$	11,199
Partners' capital		126,548		133,328

Total liabilities and partners' capital	$	140,481	$	144,527

LSV Employee Group

At the time of LSV Employee Group's purchase of an eight percent interest in LSV, it was determined that $72,220 of the purchase price related to identifiable intangible assets and $19,780 was goodwill. The identifiable intangible assets have an estimated useful life of ten years and were amortized on a straight-line basis. Prior to the deconsolidation of LSV Employee Group from the Company's financial statements, amortization expense in 2009 on the accompanying Consolidated Statement of Operations included $7,222 pertaining to the amortization of the intangible assets, but was eliminated through Noncontrolling interest and had no impact on net income.

In order to finance a portion of the purchase price, LSV Employee Group obtained financing from Bank of America, N.A. (Bank of America) and certain other lenders in the form of a term loan pursuant to the terms of a Credit Agreement. The principal amount of the term loan was $82,800. In January 2011, LSV Employee Group and Bank of America agreed to amend the Credit Agreement and extend the maturity date of the loan from January 2011 to July 2012. The Company's obligations under the Guaranty Agreement remained in full force and effect with respect to the amended Credit Agreement. LSV Employee Group made the final principal payment of the term loan in October 2011 and the Company has no further obligation regarding the Credit Agreement. LSV Employee Group made principal payments of $10,091 and $10,461 during 2011 and 2010.

Prior to the deconsolidation of LSV Employee Group from the Company's financial statements, interest expense in 2009 on the Consolidated Statement of Operations includes $1,510 in interest costs related to the term loan which were eliminated through Noncontrolling interest and had no impact on net income.

LSV Employee Group II

In April 2011, a group of existing employees of LSV agreed to purchase a partnership interest of an existing LSV employee for $4,300 of which $3,655 was financed through a new term loan with Bank of America. The group of existing LSV employees formed a new limited liability company, LSV Employee Group II, LLC (LSV Employee Group II). The Company provided an unsecured guaranty to the lenders of all the obligations of LSV Employee Group II. The lenders will have the right to seek payment from the Company in the event of a default by LSV Employee Group II. The term loan has a four year term and will be repaid from the quarterly distributions of LSV. LSV Employee Group II made principal payments of $458 during 2011. As of December 31, 2011, the remaining unpaid principal balance of the term loan was $3,197. This amount is not reflected, nor is it required to be reflected, in the Company's Consolidated Balance Sheet at December 31, 2011.

The Company's direct interest in LSV was unchanged as a result of this transaction. The Company has determined that LSV Employee Group II is a variable interest entity (VIE); however, the Company is not considered the primary beneficiary because it does not have the power to direct the activities that most significantly impact the economic performance of LSV Employee Group II either directly or through any financial responsibility from the guaranty.

In January 2012, LSV Employee Group II made a principal payment of $219. As of January 31, 2012, the remaining unpaid principal balance of the term loan was $2,978. The Company, in its capacity as guarantor, currently has no obligation of payment relating to the term loan of LSV Employee Group II and, furthermore, fully expects that LSV Employee Group II will meet all of their future obligations regarding the term loan.

Proforma Financial Information (Unaudited)

The unaudited proforma financial information for the year ended December 31, 2009 presents the historical results of the Company as if the accounts and operations of LSV and LSV Employee Group had not been consolidated and LSV had been accounted for under the equity method. Net income attributable to SEI was unchanged due to this transaction but is presented for the purpose of clarification.


Proforma Unaudited Condensed Statement of Operations Year ended December 31,	2009

Revenues	$	848,587
Expenses		(658,434	)


Income from operations		190,153

Other income, net		87
Equity in the earnings of unconsolidated affiliate		75,415


Net income before income taxes		265,655
Income taxes		89,886


Net income		175,769


Less: Net income attributable to the noncontrolling interest		(1,434	)


Net income attributable to SEI Investments	$	174,335

Variable Interest Entities - Investment Products	12 Months Ended
Variable Interest Entities - Investment Products	Dec. 31, 2011
Variable Interest Entities - Investment Products [Abstract]
Variable Interest Entities - Investment Products	Note 3 – Variable Interest Entities – Investment Products The Company has created numerous investment products for its clients in various types of legal entity structures. The Company serves as the Manager, Administrator and Distributor for these investment products and may also serve as the Trustee for some of the investment products. Clients are the equity investors and participate in proportion to their ownership percentage in the net income or loss and net capital gains or losses of the products, and, on liquidation, will participate in proportion to their ownership percentage in the remaining net assets of the products after satisfaction of outstanding liabilities. An entity that lacks decision-making rights is a VIE. In some circumstances, the Manager or Trustee of the Company's investment products controls the governing decisions about the investment activities with respect to the ongoing operations of the investment products without the equity investors possessing the right to remove the Manager or Trustee. Therefore, the equity investors, as a group, do not have the ability to make decisions that have an impact on the ongoing activities of such investment products. Consequently, some of the Company's investment products have been determined to be VIEs at inception. The VIEs are marketed with investment objectives to generate positive returns; however, the nature of such investments exposes the investors to the risk that the value of the VIEs may increase or decrease. The purpose and design of the VIEs are to achieve the investment objective by implementing strategies which are designed to minimize potential losses; however, there is no assurance given that these strategies will be successful. The Company does not have a significant equity investment in any of the VIEs and does not have an obligation to enter into any guarantee agreements with the VIEs. The fees paid to the decision maker of a VIE are considered to be variable interests if the decision maker is not subject to substantive kick-out rights. The fees paid to the Company represent a variable interest when the decision maker is not subject to substantive kick-out rights. The Company is not the primary beneficiary of the VIEs because the expected fees and the expected return on any investment into the VIE by the Company relative to the expected returns of the VIE to the equity investor holders does not approach 50 percent of the expected losses or gains of the VIEs. Therefore, the Company is not required to consolidate any investment products that are VIEs into its financial statements. The Company's variable interest in the VIEs, which consists of management fees and in some situations, seed capital, would not be considered a significant variable interest. The risks to the Company associated with its involvement with any of the investment products that are VIEs are limited to the cash flows received from the revenue generated for asset management, administration and distribution services and any equity investments in the VIEs. Both of these items are immaterial. The Company has no other financial obligation to the VIEs. Amounts relating to fees received from the VIEs included in Receivables and amounts relating to equity investments in the VIEs included in Investments Available for Sale on the Company's Consolidated Balance Sheets are immaterial to the total current assets of the Company.

Composition Of Certain Financial Statement Captions

12 Months Ended

Dec. 31, 2011

Composition Of Certain Financial Statement Captions [Abstract]

Composition Of Certain Financial Statement Captions

Note 4 – Composition of Certain Financial Statement Captions

Receivables

Receivables on the accompanying Consolidated Balance Sheets consist of:


	2011			2010
Trade receivables	$	37,822		$	34,528
Fees earned, not billed		92,916			93,506
Other receivables		12,295			9,651


		143,033			137,685

Less: Allowance for doubtful accounts		(924	)		(1,195	)


Receivables, net	$	142,109		$	136,490

Fees earned, not billed represents receivables earned but unbilled and results from timing differences between services provided and contractual billing schedules. These billing schedules generally provide for fees to be billed on a quarterly basis.

Receivables from regulated investment companies on the accompanying Consolidated Balance Sheets primarily represent fees receivable for distribution, investment advisory, and administration services to various regulated investment companies sponsored by SEI (See Note 14).

Property and Equipment

Property and Equipment on the accompanying Consolidated Balance Sheets consists of:


	2011			2010

Buildings	$	136,949		$	135,935
Equipment		64,256			63,902
Land		9,929			9,890
Purchased software		77,971			74,720
Furniture and fixtures		17,999			18,566
Leasehold improvements		4,558			4,250
Construction in progress		339			121


		312,001			307,384

Less: Accumulated depreciation		(182,453	)		(166,816	)


Property and Equipment, net	$	129,548		$	140,568

Depreciation expense related to property and equipment for 2011, 2010, and 2009 was $21,471, $21,902, and $21,531, respectively.

Other Assets

Other assets consist of long-term prepaid expenses, deposits, other investments at cost and various other assets. Amortization expense for certain other assets for 2011, 2010, and 2009 was $1,135, $995 and $1,055, respectively.

The Company recognized gains of $3,072 in 2010 due to the sale of its entire ownership interest in a small, private company that was involved in a merger. The Company's investment in the firm had been accounted for under the cost basis. The gain is reflected in Net gain (loss) on investments on the accompanying Consolidated Statements of Operations.

Accrued Liabilities

Accrued Liabilities on the accompanying Consolidated Balance Sheets consist of:


	2011		2010

Accrued employee compensation	$	48,112	$	43,747
Accrued employee benefits and other personnel		5,408		6,988
Accrued consulting, outsourcing and professional fees		17,477		16,390
Accrued brokerage fees		8,665		11,942
Accrued sub-advisory, distribution and other asset management fees		17,091		16,778
Accrued income taxes		0		2,077
Accrued dividend payable		26,518		0
Other accrued liabilities		23,773		23,488


Accrued liabilities	$	147,044	$	121,410

Fair Value Measurements

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Fair Value Measurements

Note 5 – Fair Value Measurements

The fair value of the Company's financial assets and liabilities is determined in accordance with the fair value hierarchy. The fair value of the Company's financial assets, except for the fair value of senior notes issued by SIVs, is determined using Level 1 or Level 2 inputs and consist mainly of investments in equity and fixed-income mutual funds that are quoted daily and GNMA and other U.S. government agency securities that are single issuer pools that are valued based on current market data for the specific issue owned or pools of similar securities. Level 3 financial assets primarily consist of senior note obligations issued by SIVs. The Company did not have any Level 3 financial liabilities at December 31, 2011 or 2010. There were no transfers of financial assets between levels within the fair value hierarchy during 2011 or 2010.

Valuation of SIV Securities

The underlying collateral of the SIV securities is mainly comprised of asset-backed securities and collateralized debt obligations. The Company received prices for all of its SIV securities from two independent third party firms. Given the lack of any reliable market data on the SIV securities, the firms utilized a valuation model that employs a net asset approach which considers the value of the underlying collateral of the SIV securities to determine the fair value of the SIV securities. Management evaluates the prices received from these firms and considers other information, such as the existence of any current market activity, to determine the fair value of the SIV securities. The underlying collateral is specifically identified by its CUSIP or ISIN number. In January 2011, the Company sold the senior obligation originally issued by Stanfield Victoria. The Company's sole remaining SIV security consists of the senior note issued by Gryphon.

The valuation model maintained by the third party firm to value the SIV securities owned as of December 31, 2010 (except the Stanfield Victoria note) obtained price quotes for each security that comprised the underlying collateral of the SIV securities. Price quotes were primarily obtained from two pricing vendors that are independent entities of the firm that maintained the valuation model. Other pricing vendors were used in limited situations when a security quote cannot be obtained from either of the two primary pricing vendors. The average of the two quotes received was used to value each security. A portion of the securities that comprised the underlying collateral of the SIV securities could not be priced by the pricing vendors. For these securities that lack price quotes, the last price quote received was adjusted by the weighted average percentage movement of securities held as collateral within the same sector classification or based upon the weighted average movement of all priced securities. For example, a residential mortgage-backed security that has not received a quote for an extended period of time was adjusted by the weighted average percentage movement of all quoted residential mortgage-backed securities held as collateral by the SIV security. Additionally, the securities were aggregated by type or sector (i.e. home equity line of credit, sub-prime 1^st liens, residential mortgage-backed securities, etc.) and the weighted average quote of all securities within a sector held by the SIV was compared with the range of quotes received for similar securities within the same sector from the trading desk of an affiliate of the third party firm that maintains the SIV valuation model. The weighted average quote of all securities within a sector held by the SIV must be within the range of quotes received from the trading desk within that same sector. If the weighted average quote for all securities within a sector held by the SIV was outside that range, the average quote received from the pricing vendors was adjusted. In any event, the value assigned to each security held by the SIV was the lower of (i) the average of the quotes received from the pricing vendors or (ii) the lowest quote received from the trading desk for a similar security.

The pricing vendors used by the firm that maintained the valuation model utilize widely-accepted pricing models, which are evaluated by the pricing vendor, that vary by asset class and incorporate available trade, bid, and other market information. The market inputs that these pricing vendors sought for their evaluation of securities included: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and other available market data. Broker quotes may be binding or non-binding. For certain security types, additional inputs may be used. The pricing vendors may prioritize inputs differently from time to time for any security based on current market conditions. For each asset class, the pricing vendor used a team of evaluators that gathered information from market sources and integrated relevant credit information, perceived market movements and sector news into the evaluated pricing models. For a structured security evaluation, including mortgage-backed securities, these evaluators considered various characteristics including issuer, vintage, purpose of loan, collateral attributes, prepayment speeds and credit ratings in order to properly identify trades and quotes for similar securities which are gathered for use in the evaluation process. Evaluators follow multiple review processes throughout each month that assess the available market, credit and deal level information in support of the evaluation process. If it is determined that sufficient objectively verifiable information does not exist to support a security's valuation, the pricing vendor discontinued providing a quote on that security. As previously stated, securities that lack a quote from a pricing vendor are valued using the most recent quoted price and adjusting that price by the weighted average percentage change in the respective sector of all other similar securities that are held by the SIV.

The model used by the second independent valuation firm to determine the fair value of the Stanfield Victoria note as of December 31, 2010 and the Gryphon Note as of December 31, 2011 also utilized a net asset approach that attempts to value the underlying collateral of the SIV securities through the use of industry accepted and proprietary valuation techniques and models. This approach combines advanced analytics with real-time market information that incorporate structural and fundamental analysis, collateral characteristics, recent market developments and current trading activity for each security. Each security that makes up the underlying collateral is analyzed by using observable collateral characteristics and credit statistics in order to project future performance and expected cash flows for each individual security. The projected cash flows incorporate assumptions and expectations based upon the foregoing analysis of the collateral characteristics such as, but not limited to, default probabilities, recovery rates, prepayment speeds and loss severities. Expected future cash flows are discounted at an appropriate yield derived from the individual security, structural and collateral characteristics, trading levels and other available market data. Different modeling techniques and associated inputs and assumptions may be used to project future cash flows for each security depending upon the asset classification of that individual security (i.e. residential mortgage-backed security, commercial mortgage-backed security, collateralized debt obligations, etc.). The aggregate value of the discounted cash flows of the underlying collateral is compared to the total remaining par value of the collateral to determine the expected recovery price, or fair value, of the remaining note obligations.

Management may also consider, when available, price quotes from brokers and dealers. If a price quote is available, management will compare this number to the fair value derived from the valuation models of the two independent firms giving consideration to other market factors and risk premiums. Given the lack of any significant trading activity for any of the SIV securities owned by the Company, management believes that market prices for any SIV securities may not represent the implied fair value of the SIV securities owned by the Company.

Management evaluates current market transactions, if any, for each of the SIV securities. In the event a market transaction does exist for a SIV security, management evaluates the publicly available information surrounding the transaction in order to assess if the price used represents the fair value for the SIV security. In management's opinion, the current market for SIV securities does not represent any orderly and efficient market.

The fair value of certain financial assets and liabilities of the Company was determined using the following inputs:


			At December 31, 2011
			Fair Value Measurements at Reporting Date Using
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)

Assets
Equity available-for-sale securities	$	8,010	$	8,010	$	0	$	0
Fixed-income available-for-sale securities		74,998		0		74,998		0
Fixed income securities owned		20,949		0		20,949		0
Trading securities		56,325		3,702		0		52,623


	$	160,282	$	11,712	$	95,947	$	52,623


			At December 31, 2010
			Fair Value Measurements at Reporting Date Using
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)

Assets
Equity available-for-sale securities	$	5,853	$	5,853	$	0	$	0
Fixed-income available-for-sale securities		68,917		0		68,917		0
Trading securities		104,594		3,949		0		100,645


	$	179,364	$	9,802	$	68,917	$	100,645

The table below presents a reconciliation for all assets and liabilities of the Company measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the period from January 1, 2010 to December 31, 2011:


	Trading Securities

Balance, January 1, 2010	$	120,714

Purchases		536
Issuances		0
Principal prepayments and settlements		(45,857	)
Sales		(18,995	)
Total gains or (losses) (realized/unrealized):
Included in earnings		44,247
Included in other comprehensive income		0
Transfers in and out of Level 3		0


Balance, December 31, 2010	$	100,645

Purchases		1,215
Issuances		0
Principal prepayments and settlements		(17,921	)
Sales		(34,706	)
Total gains or (losses) (realized/unrealized):
Included in earnings		3,390
Included in other comprehensive income		0
Transfers in and out of Level 3		0


Balance, December 31, 2011	$	52,623

- Definition

Tabular disclosure of the fair value measurement of assets and liabilities which includes [financial] instruments measured at fair value that are classified in stockholders' equity. Such assets and liabilities may be measured on a recurring or nonrecurring basis. The disclosures which may be required or desired include: (1) for assets and liabilities measured on a recurring basis, disclosure may include: (a) the fair value measurements at the reporting date; (b) the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets or liabilities (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3); (c) for fair value measurements using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (i) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (ii) purchases, sales, issuances, and settlements (net); (iii) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs); (d) the amount of the total gains or losses for the period in subparagraph (c) (i) above included in earnings (or changes in net assets) that are attributable to the change in unrealized gains or losses relating to those assets and liabilities still held at the reporting date and a description of where those unrealized gains or losses are reported in the statement of income (or activities); (e) the valuation technique(s) used to measure fair value and a discussion of changes in valuation techniques, if any, during the period and (2) for assets and liabilities that are measured at fair value on a nonrecurring basis (for example, impaired assets) disclosure may include, in addition to (a) above: (a) the reasons for the fair value measurements recorded; (b) the same as (b) above; (c) for fair value measurements using significant unobservable inputs (Level 3), a description of the inputs and the information used to develop the inputs; and (d) the valuation technique(s) used to measure fair value and a discussion of changes, if any, in the valuation technique(s) used to measure similar assets and/or liabilities in prior periods. Where the quoted price in an active market for the identical liability is not available, the Level 1 input is the quoted price of an identical liability when traded as an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 33

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 6

-Footnote 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19190-110258

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19279-110258

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19296-110258

+ Details

Marketable Securities

12 Months Ended

Dec. 31, 2011

Marketable Securities [Abstract]

Marketable Securities

Note 6 – Marketable Securities

Investments Available For Sale

Investments available for sale classified as non-current assets consist of:


	For the Year ended December 31, 2011
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SEI-sponsored mutual funds	$	8,243	$	48	$	(360	)	$	7,931
Other mutual funds		69		10		0			79
Debt securities		70,604		4,394		0			74,998


	$	78,916	$	4,452	$	(360	)	$	83,008
	For the Year Ended December 31, 2010
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SEI-sponsored mutual funds	$	5,086	$	279	$	(14	)	$	5,351
Other mutual funds		443		59		0			502
Debt securities		67,118		1,799		0			68,917


	$	72,647	$	2,137	$	(14	)	$	74,770

Net unrealized holding gains were $2,574 (net of income tax expense of $1,518) at December 31, 2011. At December 31, 2010, net unrealized holding gains were $1,339 (net of income tax expense of $784). These unrealized gains are reported as separate components of Accumulated other comprehensive income on the accompanying Consolidated Balance Sheets.

The Company recognized gross realized gains from available-for-sale securities of $255, $184 and $440 in 2011, 2010 and 2009, respectively. Gross realized losses in 2009 were $123. Gross realized losses in 2011 and 2010 were minimal.

The Company had investments in two SEI-sponsored mutual funds which primarily invest in fixed-income securities, including debt securities issued by municipalities and mortgage-backed securities. In 2009, management determined that the decline in market value for one of these mutual funds was other-than-temporary and, therefore, recorded an impairment charge for $901. The other-than-temporary impairment charge is included in Net gain (loss) on investments on the Consolidated Statements of Operations.

The Company's debt securities are issued by the Government National Mortgage Association and are backed by the full faith and credit of the U.S. government. These securities were purchased to satisfy applicable regulatory requirements of SPTC and have maturity dates which range from 2020 to 2041.

Trading Securities

Trading securities of the Company consist of:


	For the Year ended December 31, 2011
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SIV securities	$	146,363	$	0	$	(94,955	)	$	51,408
LSV-sponsored mutual funds		2,049		1,653		0			3,702
Other investments		1,215		0		0			1,215


	$	149,627	$	1,653	$	(94,955	)	$	56,325
	For the Year ended December 31, 2010
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SIV securities	$	231,026	$	0	$	(130,381	)	$	100,645
LSV-sponsored mutual funds		2,049		1,900		0			3,949


	$	233,075	$	1,900	$	(130,381	)	$	104,594

The Company records all of its trading securities on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these securities are recognized in Net gain (loss) from investments on the accompanying Consolidated Statements of Operations.

During 2011 and 2010, the Company recognized net gains from SIV securities of $3,390 and $44,247, respectively. Of the net gains recognized during 2011, gains of $10,614 resulted from cash payments received from the SIV securities offset by losses of $7,224 which resulted from a decrease in fair value at December 31, 2011. During 2010, the Company recognized gains from SIV securities of $44,247, of which $27,510 resulted from cash payments received from the SIV securities and $16,460 was from a net increase in fair value at December 31, 2010. In addition, the Company recognized a net gain of $277 from sales of three SIV securities during 2010. The cumulative loss recognized by the Company pertaining to these SIV securities sold in 2010 was $17,944. The net gains (losses) from the SIV securities are reflected in Net gain (loss) from investments on the accompanying Consolidated Statements of Operations.

In January 2011, the Company sold the senior note obligation originally issued by Stanfield Victoria. There was no gain or loss recognized by the Company from the sale of the note as the fair value of the Stanfield Victoria note at December 31, 2010 was not different than the sale price received. Currently, the Company's remaining SIV security consists of the senior note obligation issued by Gryphon.

The Company has an investment related to the startup of mutual funds sponsored by LSV. These are U.S. dollar denominated funds that invests primarily in securities of Canadian, Australian and Japanese companies as well as various other global securities. The underlying securities held by the funds are translated into U.S. dollars within the funds. During the three months ended June 30, 2010, the Company sold a portion of its investment in the LSV-sponsored funds. Additionally, the Company sold all of the equity and currency futures contracts originally purchased as part of an economic strategy to minimize exposure to price and currency risk related to the investment. The net gains recognized from the partial sale of the LSV-sponsored funds and the equity and futures contracts were minimal. As of December 31, 2011, the Company's remaining investment in the LSV-sponsored funds had a cost value of $2,049 and a fair value of $3,702.

Securities Owned

During 2011, the Company's broker-dealer subsidiary, SIDCO, made investments in U.S. government agency and commercial paper securities with maturity dates less than one year. These investments are reflected as Securities owned on the accompanying Consolidated Balance Sheets. Due to specialized accounting practices applicable to investments by broker-dealers, the securities are reported at fair value and changes in fair value are recorded in current period earnings. The securities had a fair value of $20,949 at December 31, 2011. The change in fair value of the securities recognized in 2011 was minimal.

- Definition

Tabular disclosure of marketable securities. This may consist of investments in certain debt and equity securities, short-term investments and other assets.

+ References+ Details

Lines Of Credit	12 Months Ended
Lines Of Credit	Dec. 31, 2011
Lines Of Credit [Abstract]
Lines Of Credit	Note 7 – Lines of Credit: The Company maintained a $300,000 revolving line of credit through a Credit Agreement (Credit Facility), as amended, with JPMorgan Chase Bank, N.A. and a syndicate of other lenders which was scheduled to expire in July 2012. Outstanding borrowings under the Credit Facility accrued interest at 0.450 percent above the London Interbank Offer Rate (LIBOR) during 2011. There was also a commitment fee equal to 0.09 percent per annum on the daily unused portion of the facility charged to the Company during 2011. The Credit Facility, as amended, contained covenants that restricted the ability of the Company to engage in mergers, consolidations, asset sales, investments, transactions with affiliates, or to incur liens, as defined in the agreement. None of the covenants of the Credit Facility negatively affected the Company's liquidity or capital resources. As of December 31, 2011, the Company's ability to borrow from the Credit Facility was not limited by any covenant of the agreement. In 2009, the Company borrowed $254,000 from the Credit Facility to finance the purchase of SIV securities from SEI-sponsored money market mutual funds (See Note 6). The Company made principal payments of $95,000, $138,000 and $21,000 during 2011, 2010 and 2009, respectively, to fully repay the outstanding balance of the Credit Facility. The Company was in compliance with all covenants of the Credit Facility during 2011. The average rates applied to the Credit Facility during 2011, 2010 and 2009 were 0.68 percent, 0.77 percent and 1.05 percent, respectively. The Company incurred $585, $1,478, and $2,491 in interest charges and commitment fees relating to the Credit Facility during 2011, 2010, and 2009, respectively, which are reflected in Interest expense on the accompanying Consolidated Statements of Operations. The Company considers the book value of long-term debt on the accompanying Consolidated Balance Sheet at December 31, 2010 related to the borrowings through the Credit Facility to be representative of its fair value. The Company had no borrowings through the Credit Facility at December 31, 2011. On February 2, 2012 (the Closing Date), the Company terminated the Credit Facility agreement and entered into a new five-year $300,000 Credit Agreement (the 2012 Credit Facility) with Wells Fargo Bank, National Association, and a syndicate of other lenders. The 2012 Credit Facility became available on the Closing Date and is scheduled to expire in February 2017, at which time any aggregate principal amount of loans outstanding becomes payable in full. Any borrowings made under the 2012 Credit Facility will accrue interest at 1.250 percent above LIBOR. There is also a commitment fee equal to 0.15 percent per annum on the daily unused portion of the facility. The aggregate amount of the 2012 Credit Facility may be increased by an additional $100,000 under certain conditions set forth in the agreement. The 2012 Credit Facility contains covenants that restrict the ability of the Company to engage in mergers, consolidations, asset sales, investments, transactions with affiliates, or to incur liens, as defined in the agreement. In the event of a default under the 2012 Credit Facility, the Company would also be restricted from paying dividends on, or repurchasing, its common stock without the approval of the lenders. None of the covenants of the 2012 Credit Facility negatively affect the Company's liquidity or capital resources. Both the interest rate and commitment fee prices may increase if the Company's leverage ratio reaches certain levels. Upon the occurrence of certain financial or economic events, significant corporate events, or certain other events of default constituting an event of default under the 2012 Credit Facility, all loans outstanding may be declared immediately due and payable and all commitments under the 2012 Credit Facility may be terminated. The Company's Canadian subsidiary has a credit facility agreement (the Canadian Credit Facility) for the purpose of facilitating the settlement of mutual fund transactions. The Canadian Credit Facility has no stated expiration date. The amount of the facility is generally limited to $2,000 Canadian dollars or the equivalent amount in U.S. dollars. The Canadian Credit Facility does not contain any covenants which restrict the liquidity or capital resources of the Company. The Company had no borrowings under the Canadian Credit Facility and was in compliance with all covenants during 2011.

Shareholders' Equity

12 Months Ended

Dec. 31, 2011

Shareholders' Equity [Abstract]

Shareholders' Equity

Note 8 – Shareholders' Equity:

Stock-Based Compensation

The Company currently has one active equity compensation plan, the 2007 Equity Compensation Plan (the 2007 Plan), which provides for the grant of incentive stock options, non-qualified stock options and stock appreciation rights with respect to up to 20 million shares of common stock of the Company, subject to adjustment for stock splits, reclassifications, mergers and other events. Permitted grantees under the 2007 Plan include employees, non-employee directors and consultants who perform services for the Company. The plan is administered by the Compensation Committee of the Board of Directors of the Company. The Company has only granted non-qualified stock options under the plan.

The Company discontinued any further grants under the Company's 1998 Equity Compensation Plan (the 1998 Plan) as a result of the approval of the 2007 Plan. No options are available for grant from this plan. Grants made from the 1998 Plan continue in effect under the terms of the grant.

All outstanding stock options have performance-based vesting provisions that tie the vesting of stock options to the Company's financial performance. The Company's stock options vest at a rate of 50 percent when a specified diluted earning per share target is achieved, and the remaining 50 percent when a second, higher specified diluted earnings per share target is achieved. Stock options granted prior to 2006 fully vest after seven years from the date of grant. Beginning in 2006, the seven year vesting trigger was eliminated and, as a result, options do not vest due to the passage of time but solely as a result of achievement of the financial vesting targets. Earnings per share targets are calculated exclusive of stock-based compensation expense, net of tax. The diluted earnings per share targets are established at time of grant and are measured annually on December 31. The amount of stock-based compensation expense is based upon management's estimate of when the earnings per share targets may be achieved. If management's estimate of the attainment of the earnings per share targets proves to be inaccurate, the remaining amount of stock-based compensation expense could be accelerated, spread out over a longer period, or reversed. This may cause volatility in the recognition of stock-based compensation expense in future periods and could materially affect the Company's net income and net income per share.

The Company uses the Black-Scholes option pricing model to determine the fair value of stock options. The determination of the fair value of stock options on the date of grant using an option-pricing model is affected by the price of the Company's common stock as well as other variables. These variables include expected stock price volatility over the term of the awards, actual and projected employee stock exercise behaviors, risk-free interest rate and expected dividends. The Company primarily uses historical data to estimate the variables used in the option-pricing model except expected volatility. The Company uses a combination of historical and implied volatility. The Company estimates forfeitures at the time of grant and may revise those estimates in subsequent periods if actual forfeitures differ from those estimates. The Company uses historical data to estimate pre-vesting forfeitures and record stock-based compensation expense only for those awards that are expected to vest. Stock-based compensation is amortized over the requisite service periods of the awards, which are generally the vesting periods.

The weighted average fair value of the Company's stock options granted during 2011, 2010 and 2009 were $5.70, $9.65 and $7.24, respectively, using the following assumptions:


	2011			2010			2009

Expected term (in years)		7.65			7.45			7.49
Expected volatility		40.43	%		36.35	%		37.44	%
Expected dividend yield		1.90	%		0.84	%		1.02	%
Risk-free interest rate		1.66	%		3.01	%		3.31	%

The Company recognized stock-based compensation expense in its Consolidated Financial Statements in 2011, 2010 and 2009 as follows:


	2011			2010			2009

Stock-based compensation expense	$	14,112		$	26,783		$	14,503
Less: Deferred tax benefit		(5,332	)		(10,068	)		(4,636	)


Stock-based compensation expense, net of tax	$	8,780		$	16,715		$	9,867

During 2010, the Company revised its estimates of when some vesting targets are expected to be achieved. These changes in management's estimates resulted in an increase of $11,663 in stock-based compensation expense in 2010. Additionally, during the three months ended September 30, 2010, the Company reversed $6,375 of previously-recognized stock-based compensation costs pertaining to option grants which management does not expect to vest. Management does not expect to recognize any compensation cost associated with these option grants. As of December 31, 2010, these option grants have an unrecognized compensation cost of $27,460.

The Company reduced the amount of stock-based compensation expense recognized in 2009 by $8,223 due to a change in management's estimate of when certain vesting targets are expected to be achieved.

As of December 31, 2011, there was approximately $48,123 of unrecognized compensation cost remaining, adjusted for estimated forfeitures, related to unvested employee stock options that the Company expects will vest. The Company estimates that compensation cost will be recognized according to the following schedule:


Period	Stock-Based Compensation Expense

2012	$	14,398
2013		12,704
2014		12,510
2015		3,846
2016		2,355
2017		2,310


	$	48,123

This table presents certain information relating to the Company's stock option plans for 2011, 2010, and 2009:


	Number of Shares			Weighted Avg. Price

Balance as of December 31, 2008		28,883,000		$	19.90
Granted		4,222,000			17.66
Exercised		(2,055,000	)		10.53
Expired or canceled		(2,086,000	)		21.87


Balance as of December 31, 2009		28,964,000		$	20.09
Granted		2,883,000			23.84
Exercised		(1,633,000	)		16.04
Expired or canceled		(2,333,000	)		23.68


Balance as of December 31, 2010		27,881,000		$	20.42
Granted		2,534,000			15.77
Exercised		(1,364,000	)		16.37
Expired or canceled		(2,008,000	)		22.07


Balance as of December 31, 2011		27,043,000		$	20.06

Exercisable as of December 31, 2011		11,680,000		$	17.22

Available for future grant as of December 31, 2011		4,622,000

As of December 31, 2010 and 2009, there were 14,247,000 and 11,801,000 shares exercisable, respectively. The expiration dates for options outstanding at December 31, 2011 range from December 10, 2012 to December 13, 2021 with a weighted average remaining contractual life of 5.9 years.

Upon exercise of stock options, the Company will issue new shares of its common shares. The Company does not hold any shares in treasury. The total intrinsic value of options exercised during 2011 and 2010 was $8,642 and $9,961, respectively. The aggregate intrinsic value of options exercisable as of December 31, 2011 was $1,534. The total options outstanding as of December 31, 2011 had no aggregate intrinsic value due to the fact that the weighted average exercise price exceeded the market value of the Company's common stock. The total intrinsic value for options outstanding and options exercisable is calculated as the difference between the market value of the Company's common stock as of December 31, 2011 and the exercise price of the shares. The market value of the Company's common stock as of December 31, 2011 was $17.35 as reported by the Nasdaq Stock Market, LLC.

This table summarizes information relating to all options outstanding and exercisable at December 31, 2011:


	Options Outstanding at December 31, 2011						Options Exercisable at December 31, 2011
Range of Exercise Prices (Per Share)	Number of Shares		Weighted Average Exercise Price (Per Share)		Weighted Average Remaining Contractual Life (Years)		Number of Shares		Weighted Average Exercise Price (Per Share)		Weighted Average Remaining Contractual Life (Years)

$14.05 – 14.71		5,285,000	$	14.65		5.28		3,296,000	$	14.66		4.24
14.78 – 17.35		5,179,000		15.30		6.00		2,642,000		14.84		2.17
17.65 – 19.28		6,560,000		18.33		6.33		3,165,000		18.32		6.37
19.53 – 23.86		5,375,000		22.75		6.13		2,562,000		21.55		3.00
27.03 – 32.49		4,644,000		30.88		5.46		15,000		27.03		5.00


		27,043,000						11,680,000

As of December 31, 2011 and 2010, there was $142,872 and $141,438, respectively, available in the pool of windfall tax benefits.

Employee Stock Purchase Plan

The Company has an employee stock purchase plan that provides for offerings of common stock to eligible employees at a price equal to 85 percent of the fair market value of the stock at the end of the stock purchase period, as defined. The Company has reserved 15,600,000 shares for issuance under this plan. At December 31, 2011, 11,474,000 cumulative shares have been issued. Costs incurred by the Company related to the employee stock purchase plan were immaterial in 2011, 2010 and 2009.

Common Stock Buyback

The Board of Directors, under multiple authorizations, has authorized the purchase of the Company's common stock on the open market or through private transactions. As of January 31, 2012, the Company had approximately $95,823 of authorization remaining for the purchase of common stock. The following table provides the total number of shares repurchased and the related total costs in 2011, 2010 and 2009:


Year	Total Number of Shares Repurchased		Total Cost

2011		11,109,000	$	211,165
2010		5,814,000		120,982
2009		3,198,000		54,114

The Company immediately retires its common stock when purchased. Upon retirement, the Company reduces Capital in excess of par value for the average capital per share outstanding and the remainder is charged against Retained earnings. If the Company reduces its Retained earnings to zero, any subsequent purchases of common stock will be charged entirely to Capital in excess of par value.

Rights Agreement

In December 2008, the Company's Board of Directors declared a dividend distribution pursuant to a Rights Agreement (the Rights Agreement) which became effective on January 6, 2009. The purpose of the Rights Agreement is to deter coercive or unfair takeover tactics and to prevent a person or group (an Acquiring Person) from acquiring control of the Company without offering a fair price to all shareholders. Under the Rights Agreement, all common shareholders receive one Right for each common share outstanding. Each Right entitles the registered holder to purchase from the Company a unit consisting of one twenty-thousandths of a share of Series A Junior Participating Preferred Shares, $.05 par value per share, or a combination of securities and assets of equivalent value, at a purchase price of $150.00 per unit, subject to adjustment. The Rights will become exercisable and trade separately from the common stock ten days following a public announcement that an Acquiring Person has beneficial ownership of more than 20 percent of the outstanding common stock of the Company or the commencement of a tender or exchange offer that would result in an Acquiring Person owning 20 percent or more of the outstanding common stock of the Company. Upon exercise, holders, other than an Acquiring Person, will have the right to purchase the common stock of the Company equal to twice the value of the exercise price of the Rights. In lieu of requiring payment of the purchase price upon exercise of the Rights following certain events, the Company may permit the holders simply to surrender the Rights, in which event they will be entitled to receive common shares and other property, as the case may be, with a value of 50 percent of what could be purchased by payment of the full purchase price. The Rights, which do not have voting rights, will expire on January 6, 2019, and may be redeemed by the Company any time until ten days following the announcement of an Acquiring Person at a price of $.01 per Right.

Cash Dividends

On May 25, 2011, the Board of Directors declared a cash dividend of $.12 per share on the Company's common stock, which was paid on June 28, 2011, to shareholders of record on June 20, 2011. On December 13, 2011, the Board of Directors declared a cash dividend of $.15 per share on the Company's common stock, which was paid on January 6, 2012, to shareholders of record on December 28, 2011.

The cash dividends declared in 2011, 2010, and 2009 were $48,558, $37,513, and $32,422, respectively. The Board of Directors has indicated its intention to declare future cash dividends on a semiannual basis.

Noncontrolling Interest

The following table provides a reconciliation of Noncontrolling interest on the Consolidated Statements of Changes in Equity:


Year Ended December 31,	2011			2010			2009

Noncontrolling interest
Beginning balance	$	15,155		$	121,895		$	109,722
Net income attributable to noncontrolling interest		1,691			1,633			98,097
Foreign currency translation adjustments		(703	)		685			1,797
Deconsolidation of LSV		0			(65,522	)		0
Deconsolidation of LSV Employee Group		0			(43,536	)		0
Distributions to noncontrolling interests		0			0			(87,337	)
Other		0			0			(384	)

Ending balance	$	16,143		$	15,155		$	121,895

- Definition

The entire disclosure for shareholders' equity, comprised of portions attributable to the parent entity and noncontrolling interest, if any, including other comprehensive income (as applicable). Including, but not limited to: (1) balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings; (2) accumulated balance for each classification of other comprehensive income and total amount of comprehensive income; (3) amount and nature of changes in separate accounts, including the number of shares authorized and outstanding, number of shares issued upon exercise and conversion, and for other comprehensive income, the adjustments for reclassifications to net income; (4) rights and privileges of each class of stock authorized; (5) basis of treasury stock, if other than cost, and amounts paid and accounting treatment for treasury stock purchased significantly in excess of market; (6) dividends paid or payable per share and in the aggregate for each class of stock for each period presented; (7) dividend restrictions and accumulated preferred dividends in arrears (in aggregate and per share amount); (8) retained earnings appropriations or restrictions, such as dividend restrictions; (9) impact of change in accounting principle, initial adoption of new accounting principle and correction of an error in previously issued financial statements; (10) shares held in trust for Employee Stock Ownership Plan (ESOP); (11) deferred compensation related to issuance of capital stock; (12) note received for issuance of stock; (13) unamortized discount on shares; (14) description, terms, and number of warrants or rights outstanding; (15) shares under subscription and subscription receivables, effective date of new retained earnings after quasi-reorganization and deficit eliminated by quasi-reorganization and, for a period of at least ten years after the effective date, the point in time from which the new retained dates; and (16) retroactive effective of subsequent change in capital structure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(d),(e))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 4

-Subparagraph (SAB TOPIC 4.C)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187143-122770

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section C

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 4.E)

-URI http://asc.fasb.org/extlink&oid=6228006&loc=d3e74512-122707

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29-31)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 5

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-Name Accounting Standards Codification

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-SubTopic 10

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-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Preferred Stock

-URI http://asc.fasb.org/extlink&oid=6521494

Reference 14: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 15: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 16: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 17: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph d

Reference 18: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Chapter 1

-Section B

-Paragraph 7, 11A

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 19: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 3, 4, 5, 6, 7, 8

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 20: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Article 4

Reference 21: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 22: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

Reference 23: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section E

+ Details

Accumulated Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2011

Accumulated Comprehensive Income (Loss) [Abstract]

Accumulated Comprehensive Income (Loss)

Note 9 – Accumulated Comprehensive Income (Loss)

Comprehensive income consists of net income and other gains and losses affecting shareholders' equity that are excluded from net income. For the Company, comprehensive income includes unrealized gains and losses on available for sale securities and foreign currency translation adjustments. The Company presents comprehensive income in its Consolidated Statements of Comprehensive Income. Components of Accumulated other comprehensive income (loss) consisted of:


	Foreign Currency Translation Adjustments			Unrealized Holding Gains (Losses) On Investments			Accumulated Other Comprehensive Income (Loss)
Total accumulated comprehensive loss at January 1, 2009	$	(9,787	)	$	(1,524	)	$	(11,311	)

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at January 1, 2009		3,148			0			3,148


Total accumulated comprehensive loss attributable to SEI Investments Company at January 1, 2009	$	(6,639	)	$	(1,524	)	$	(8,163	)

Total comprehensive income		8,734			2,484			11,218

Less: Total comprehensive income attributable to noncontrolling interest		(1,797	)		0			(1,797	)


Total comprehensive income attributable to SEI Investments Company	$	6,937		$	2,484		$	9,421

Total accumulated comprehensive income (loss) at December 31, 2009		(1,053	)		960			(93	)

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at December 31, 2009		1,351			0			1,351


Total accumulated comprehensive income attributable to SEI Investments Company at December 31, 2009	$	298		$	960		$	1,258

Total comprehensive income		2,205			379			2,584

Less: Total comprehensive income attributable to noncontrolling interest		(685	)		0			(685	)


Total comprehensive income attributable to SEI Investments Company	$	1,520		$	379		$	1,899

Total accumulated comprehensive income at December 31, 2010		1,152			1,339			2,491

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at December 31, 2010		666			0			666


Total accumulated comprehensive income attributable to SEI Investments Company at December 31, 2010	$	1,818		$	1,339		$	3,157
Total comprehensive loss		(3,195	)		1,235			(1,960	)

Less: Total comprehensive loss attributable to noncontrolling interest		703			0			703


Total comprehensive loss attributable to SEI Investments Company	$	(2,492	)	$	1,235		$	(1,257	)

Total accumulated comprehensive income at December 31, 2011		(2,043	)		2,574			531

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at December 31, 2011		1,369			0			1,369


Total accumulated comprehensive income attributable to SEI Investments Company at December 31, 2011	$	(674	)	$	2,574		$	1,900

- Definition

The entire disclosure for comprehensive income. Includes, but is not limited to, the following: 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income. Components of comprehensive income include: (1) foreign currency translation adjustments; (2) gains (losses) on foreign currency transactions that are designated as, and are effective as, economic hedges of a net investment in a foreign entity; (3) gains (losses) on intercompany foreign currency transactions that are of a long-term-investment nature, when the entities to the transaction are consolidated, combined, or accounted for by the equity method in the reporting enterprise's financial statements; (4) change in the market value of a futures contract that qualifies as a hedge of an asset reported at fair value; (5) unrealized holding gains (losses) on available-for-sale securities and that resulting from transfers of debt securities from the held-to-maturity category to the available-for-sale category; (6) a net loss recognized as an additional pension liability not yet recognized as net periodic pension cost; and (7) the net gain (loss) and net prior service cost or credit for pension plans and other postretirement benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 14-26

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e637-108580

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-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e681-108580

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-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e653-108580

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-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

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-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e709-108580

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-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 55

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6920433&loc=d3e998-108581

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e640-108580

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Reclassification Adjustments

-URI http://asc.fasb.org/extlink&oid=6522872

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e716-108580

+ Details

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2011
Employee Benefit Plan [Abstract]
Employee Benefit Plan	Note 10 – Employee Benefit Plan: The Company has a tax-qualified defined contribution plan (the Plan). The Plan provides retirement benefits, including provisions for early retirement and disability benefits, as well as a tax-deferred savings feature. After satisfying certain requirements, participants are vested in employer contributions at the time the contributions are made. All Company contributions are discretionary and are made from available profits. The Company contributed $4,783, $4,496, and $4,327 to the Plan in 2011, 2010, and 2009, respectively.

- Definition

The entire disclosure for pension and other postretirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Implementation Guide (Q and A)

-Number FAS88

-Paragraph 63

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-URI http://asc.fasb.org/topic&trid=2235017

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 158

-Paragraph 7, 21, 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5, 6, 7, 8

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph q

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 8

-Subparagraph m

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 106

-Paragraph 518

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 264

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 03-2

-Paragraph 8

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 13: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 30

-Paragraph 26

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 14: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS106-2

-Paragraph 20, 21, 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Commitments And Contingencies

12 Months Ended

Dec. 31, 2011

Commitments And Contingencies [Abstract]

Commitments And Contingencies

Note 11 – Commitments and Contingencies:

The Company leases certain of its facilities, data processing equipment, and software under non-cancelable operating leases, some which contain escalation clauses for increased taxes and operating expenses. The Company has entered into maintenance agreements primarily for its data processing equipment. Rent expense was $19,760, $17,210, and $19,022 in 2011, 2010, and 2009, respectively.

The aggregate noncancellable minimum commitments at December 31, 2011 are:


2012	$	17,892
2013		13,527
2014		6,997
2015		1,955
2016 and thereafter		10,419


	$	50,790

In the ordinary course of business, the Company from time to time enters into contracts containing indemnification obligations of the Company. These obligations may require the Company to make payments to another party upon the occurrence of certain events including the failure by the Company to meet its performance obligations under the contract. These contractual indemnification provisions are often standard contractual terms of the nature customarily found in the type of contracts entered into by the Company. In many cases, there are no stated or notional amounts included in the indemnification provisions. There are no amounts reflected on the Consolidated Balance Sheets as of December 31, 2011 and 2010 related to these indemnifications.

In the normal course of business, the Company is party to various claims and legal proceedings.

One of SEI's principal subsidiaries, SIDCO, has been named as a defendant in certain putative class action complaints (the Complaints) related to leveraged exchange traded funds (ETFs) advised by ProShares Advisors, LLC. The first complaint was filed on August 5, 2009. To date, the Complaints have been filed in the United States District Court for the Southern District of New York and in the United States District Court for the District of Maryland. The three complaints filed in the District of Maryland have been voluntarily dismissed by the plaintiffs. Two of them were subsequently re-filed in the Southern District of New York. Two of the complaints filed in the Southern District of New York have also been voluntarily dismissed by plaintiffs. The Complaints are purportedly made on behalf of all persons that purchased or otherwise acquired shares in various ProShares leveraged ETFs pursuant or traceable to allegedly false and misleading registration statements, prospectuses and statements of additional information. The Complaints name as defendants ProShares Advisors, LLC; ProShares Trust; ProShares Trust II, SIDCO, and various officers and trustees to ProShares Advisors, LLC; ProShares Trust and ProShares Trust II. The Complaints allege that SIDCO was the distributor and principal underwriter for the various ProShares leveraged ETFs that were distributed to authorized participants and ultimately shareholders. The complaints allege that the registration statements for the ProShares ETFs were materially false and misleading because they failed adequately to describe the nature and risks of the investments. The Complaints allege that SIDCO is liable for these purportedly material misstatements and omissions under Section 11 of the Securities Act of 1933. The Complaints seek unspecified compensatory and other damages, reasonable costs and other relief. Defendants have moved to consolidate the complaints, which motion has been granted. The Court appointed lead plaintiff on July 13, 2010, and an amended consolidated class action complaint was filed on September 25, 2010 asserting substantially the same claims. Defendants moved to dismiss on November 15, 2010. On December 16, 2010, lead plaintiff informed the Court and Defendants that lead plaintiff elected to file a second amended consolidated complaint, which was filed on January 31, 2011. Defendants filed a motion to dismiss the second complaint on March 17, 2011. Oral argument on this motion was held on February 2, 2012. While the outcome of this litigation is uncertain given its early phase, SEI believes that it has valid defenses to plaintiffs' claims and intends to defend the lawsuits vigorously.

SEI has been named in six lawsuits filed in Louisiana. Five lawsuits were filed in the 19th Judicial District Court for the Parish of East Baton Rouge, State of Louisiana. One of the five actions purports to set forth claims on behalf of a class and also names SPTC as a defendant. Two of the other actions also name SPTC as a defendant. All five actions name various defendants in addition to SEI, and, in all five actions, the plaintiffs purport to bring a cause of action under the Louisiana Securities Act. The putative class action originally included a claim against SEI and SPTC for an alleged violation of the Louisiana Unfair Trade Practices Act. Two of the other five actions include claims for violations of the Louisiana Racketeering Act and possibly conspiracy. In addition, another group of plaintiffs have filed a lawsuit in the 23rd Judicial District Court for the Parish of Ascension, State of Louisiana, against SEI and SPTC and other defendants asserting claims of negligence, breach of contract, breach of fiduciary duty, violations of the uniform fiduciaries law, negligent misrepresentation, detrimental reliance, violations of the Louisiana Securities Act and Louisiana Racketeering Act and conspiracy. The underlying allegations in all the actions are purportedly related to the role of SPTC in providing back-office services to Stanford Trust Company. The petitions allege that SEI and SPTC aided and abetted or otherwise participated in the sale of "certificates of deposit" issued by Stanford International Bank. Two of the five actions filed in East Baton Rouge have been removed to federal court, and plaintiffs' motions to remand are pending. These two cases have been transferred by the Judicial Panel on Multidistrict Litigation to United States District Court for the Northern District of Texas. On August 31, 2011, the United States District Court for the Northern District of Texas issued an order and judgment that the causes of action alleged against SEI and SPTC in the two remanded actions were preempted by federal law and the Court dismissed these cases with prejudice. The Court of Appeals for the Fifth Circuit has granted an expedited appeal of the United States District Court's order and judgment. The appeal has been fully briefed, and oral argument was held on February 7, 2012. The case filed in Ascension was also removed to federal court and transferred by the Judicial Panel on Multidistrict Litigation to the Northern District of Texas. The schedule for responding to that complaint has not yet been established. The plaintiffs in the remaining two cases in East Baton Rouge have granted SEI an extension to respond to the filings. SEI and SPTC filed exceptions in the putative class action pending in East Baton Rouge, which the Court granted in part and dismissed the claims under the Louisiana Unfair Trade Practices Act and denied in part as to the other exceptions. SEI and SPTC filed an answer to the East Baton Rouge putative class action; plaintiffs filed a motion for class certification; and SEI and SPTC also filed a motion for summary judgment against certain named plaintiffs which the Court stated will not be set for hearing until after the hearing on the class certification motion. Following the decision by the United States District Court for the Northern District of Texas, the Court in the East Baton Rouge action issued an order staying the proceedings in the East Baton Rouge class action pending the outcome of the appeal of the order and judgment of the United States District Court for the Northern District of Texas. While the outcome of this litigation is uncertain given its early phase, SEI and SPTC believe that they have valid defenses to plaintiffs' claims and intend to defend the lawsuits vigorously.

Because of the uncertainty of the make-up of the classes, the specific theories of liability that may survive a motion to dismiss, the lack of discovery regarding damages, causation, mitigation and other aspects that may ultimately bear upon loss, the Company is not reasonably able to provide an estimate of loss, if any, with respect to the foregoing lawsuits.

- Definition

The entire disclosure for commitments and contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 14

-Paragraph 3

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.25)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25287-109308

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6449706&loc=d3e16207-108621

+ Details

Income Taxes

12 Months Ended

Dec. 31, 2011

Income Taxes [Abstract]

Income Taxes

Note 12 – Income Taxes:

The federal and state and foreign income tax provision is summarized as follows:


Year Ended December 31,	2011			2010		2009

Current
Federal	$	99,448		$	116,388	$	16,012
State		7,067			8,698		664
Foreign		4,603			3,365		5,412


		111,118			128,451		22,088

Deferred, including current deferred
Federal		(2,317	)		6,085		61,443
State		2,477			1,509		5,822
Foreign		6			0		0


		166			7,594		67,265


Income taxes attributable to the Noncontrolling interest (1)		553			416		533

Total income taxes	$	111,837		$	136,461	$	89,886

(1)	There is no income tax provision for LSV due to its partnership structure.

Annual tax provisions include amounts considered sufficient to pay assessments that may result from examination of prior year tax returns; however, the amount ultimately paid upon resolution of issues raised may differ materially from the amount accrued. The examination and the resolution process may last longer than one year.

The components of Net income before income taxes are summarized as follows:


Year Ended December 31,	2011		2010		2009

Domestic	$	309,391	$	360,937	$	255,390
Foreign		6,852		6,795		8,300


	$	316,243	$	367,732	$	263,690

The effective income tax rate differs from the federal income tax statutory rate due to the following:


Year Ended December 31,	2011			2010			2009

Statutory rate		35.0	%		35.0	%		35.0	%
State taxes, net of Federal tax benefit		2.0			2.0			1.5
Foreign tax expense and tax rate differential		0.6			0.4			1.1
Research and development tax credit		(0.7	)		(0.5	)		(0.8	)
Domestic Production Activities Deduction		(0.7	)		0			0
Domestic Production Activities Deduction, prior years, net		(1.5	)		0			0
Net change in uncertain tax positions(2)		0.4			0.2			(2.7	)
Other, net		0.1			(0.1	)		(0.2	)


		35.2	%		37.0	%		33.9	%

(2)

For 2011, 0.25 percent relates to federal issues, 0.14 percent relates to state tax issues and the remaining 0.01 relates to foreign tax issues. For 2010, 0.14 percent relates to federal issues and the remaining 0.06 percent relates to state tax issues. For 2009, 2.0 percent relates to research and development tax credit settled with the Internal Revenue Service (IRS), 0.5 percent relates to federal issues settled with the IRS and the remaining 0.2 percent relates to state tax issues.

Undistributed earnings of the Company's foreign subsidiaries amounted to approximately $61,194 at December 31, 2011. Those earnings are considered to be indefinitely reinvested and, accordingly, no U.S. federal and state income taxes have been provided thereon. Upon distribution of those earnings, in the form of dividends or otherwise, the Company would be subject to both U.S. income taxes, subject to an adjustment for foreign tax credits, and withholding taxes payable to the various foreign countries. Determination of the amount of unrecognized deferred U.S. income tax liability is not practicable because of the complexities associated with its hypothetical calculation, including the availability, or lack thereof, of foreign tax credits to reduce a portion of the U.S. liability.

Deferred income taxes for 2011, 2010, and 2009 reflect the impact of temporary differences between the amount of assets and liabilities for financial reporting purposes and such amounts as measured by tax laws and regulations. Principal items comprising the deferred income tax provision are:


Year Ended December 31,	2011			2010			2009

Difference in financial reporting and income tax depreciation methods	$	860		$	1,381		$	(86	)
Reserves not currently deductible		651			774			394
Reserves for Capital Support Agreements and basis difference in SIV securities		(3,336	)		4,822			60,491
Capitalized software currently deductible for tax purposes, net of amortization		5,157			5,734			2,876
State deferred income taxes		1,300			1,519			2,394
Revenue and expense recognized in different periods for financial reporting and income tax purposes		(1,188	)		(562	)		(122	)
Stock-based compensation expense		(3,101	)		(7,457	)		(4,386	)
Uncertain tax positions		(182	)		(106	)		2,861
Other, net		5			1,489			2,843


	$	166		$	7,594		$	67,265

The net deferred income tax liability is comprised of:


Year Ended December 31,	2011			2010

Current deferred income taxes:
Gross assets	$	1,151		$	1,388
Gross liabilities		(1	)		(1	)

		1,150			1,387
Valuation allowance		0			0

		1,150			1,387


Long-term deferred income taxes:
Gross assets		63,374			59,892
Gross liabilities		(148,540	)		(143,137	)

		(85,166	)		(83,245	)
Valuation allowance		(8,585	)		(9,008	)

		(93,751	)		(92,253	)


Net deferred income tax liability	$	(92,601	)	$	(90,866	)

The valuation allowances against deferred tax assets at December 31, 2011 and 2010 are related to state net operating losses from certain domestic subsidiaries. Certain state tax statutes significantly limit the utilization of net operating losses for domestic subsidiaries. Furthermore, these net operating losses cannot be used to offset the net income of other subsidiaries. As of December 31, 2010, the Company fully utilized its capital loss carryforward in the amount of $4,256.

The tax effect of significant temporary differences representing deferred tax liabilities is:


Year Ended December 31,	2011			2010

Difference in financial reporting and income tax depreciation methods	$	(13,600	)	$	(11,402	)
Reserves not currently deductible		374			472
Capitalized software currently deductible for tax purposes, net of amortization		(139,455	)		(132,030	)
State deferred income taxes		6,717			5,337
Revenue and expense recognized in different periods for financial reporting and income tax purposes		3,149			3,015
Unrealized holding loss (gain) on investments		(927	)		(5,292	)
Stock-based compensation expense		43,879			40,096
State net operating loss carryforward		14,485			16,634
Valuation allowance on deferred tax assets		(8,585	)		(9,008	)
Federal benefit of state tax deduction for uncertain tax positions		1,725			1,542
Other, net		(363	)		(230	)


Net deferred income tax liability	$	(92,601	)	$	(90,866	)

The Company recognizes tax liabilities in accordance with the applicable accounting guidance and adjusts these liabilities when management's judgment changes as a result of the evaluation of new information not previously available. Due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different than from our current estimate of the tax liabilities. The Company's total unrecognized tax benefit, not including interest and penalties, as of December 31, 2011 was $9,410, of which $8,320 would affect the effective tax rate if the Company were to recognize the tax benefit. The gross amount of uncertain tax liability of $1,768 which is expected to be paid within one year is included in Current liabilities while the remaining amount of $8,276 is included in Other long-term liabilities on the accompanying Consolidated Balance Sheets. During the year ended December 31, 2011, the Company recognized $697 of previously unrecognized tax benefits relating to the lapse of the statute of limitation for certain state filings.

The Company files a consolidated federal income tax return and separate income tax returns with various states. Certain subsidiaries of the Company file tax returns in foreign jurisdictions. The Company is no longer subject to U.S. federal income tax examination for years before 2008 and is no longer subject to state, local or foreign income tax examinations by authorities for years before 2006.

A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows:


	2011			2010			2009

Balance as of January 1	$	5,723		$	4,989		$	13,453

Tax positions related to current year:
Gross additions		2,392			1,372			1,905
Gross reductions		0			0			0

		2,392			1,372			1,905

Tax positions related to prior years:
Gross additions		1,992			0			0
Gross reductions		0			(104	)		0

		1,992			(104	)		0

Settlements		0			(102	)		(9,888	)
Lapses on statute of limitations		(697	)		(432	)		(481	)


Balance as of December 31	$	9,410		$	5,723		$	4,989

The above reconciliation of the gross unrecognized tax benefit will differ from the amount which would affect the effective tax rate because of the recognition of the federal and state tax benefits.

The Company classifies all interest and penalties as income tax expense. The Company has recorded $634, $690 and $864 in liabilities for tax related interest and penalties in 2011, 2010, and 2009, respectively.

The Company estimates it will recognize $1,768 of unrecognized tax benefits within the next twelve months due to lapses on the statute of limitation.

The Company includes its direct and indirect subsidiaries in its U.S. consolidated federal income tax return. The Company's tax sharing allocation agreement provides that any subsidiary having taxable income will pay a tax liability equivalent to what that subsidiary would have paid if it filed a separate income tax return. If the separately calculated federal income tax provision for any subsidiary results in a tax loss, the current benefit resulting from such loss, to the extent utilizable on a separate return basis, is accrued and paid to that subsidiary.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Article 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 136, 172

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

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+ Details

Business Segment Information

12 Months Ended

Dec. 31, 2011

Business Segment Information [Abstract]

Business Segment Information

Note 13 – Business Segment Information:

The Company's reportable business segments are:

Private Banks – provides investment processing and investment management programs to banks and trust institutions worldwide, independent wealth advisers located in the United Kingdom, and financial advisors in Canada;

Investment Advisors – provides investment management programs to affluent investors through a network of independent registered investment advisors, financial planners, and other investment professionals in the United States;

Institutional Investors – provides investment management programs and administrative outsourcing solutions to retirement plan sponsors, hospitals, and not-for-profit organizations worldwide;

Investment Managers – provides investment operations outsourcing solutions to investment managers, fund companies and banking institutions located in the United States, and to investment managers worldwide of alternative asset classes such as hedge funds, funds of hedge funds, and private equity funds across both registered and partnership structures; and

Investments in New Businesses – provides investment management programs to ultra-high-net-worth families residing in the United States through the SEI Wealth Network® and conducts other research and development activities.

In January 2010, the Company deconsolidated the assets, liabilities and operations of LSV Asset Management. As a result, LSV is no longer considered a reportable business segment beginning in 2010.

In 2011 and 2010, no single customer accounted for more than ten percent of revenues in any business segment.

The following tables highlight certain financial information about each of the Company's business segments for the years ended December 31, 2011, 2010, and 2009:

2011


	Private Banks			Investment Advisors			Institutional Investors			Investment Managers			Investments In New Businesses			Total

Revenues	$	348,122		$	189,780		$	210,027		$	177,975		$	3,823		$	929,727
Expenses		339,339			110,438			106,585			115,963			11,559			683,884

Operating profit (loss)	$	8,783		$	79,342		$	103,442		$	62,012		$	(7,736	)	$	245,843

Profit margin		3	%		42	%		49	%		35	%		N/A			26	%

2010


	Private Banks			Investment Advisors			Institutional Investors			Investment Managers			Investments In New Businesses			Total

Revenues	$	346,668		$	183,378		$	206,531		$	160,159		$	4,099		$	900,835
Expenses		310,633			110,388			106,934			103,421			12,676			644,052

Operating profit (loss)	$	36,035		$	72,990		$	99,597		$	56,738		$	(8,577	)	$	256,783

Profit margin		10	%		40	%		48	%		35	%		N/A			29	%

2009


	Private Banks			Investment Advisors			Institutional Investors			Investment Managers			Investments In New Businesses			LSV			Total

Revenues	$	361,273		$	166,097		$	177,721		$	139,004		$	4,492		$	211,961		$	1,060,548
Expenses (1)		309,300			109,418			99,924			93,074			11,625			136,580			759,921

Operating profit (loss)	$	51,973		$	56,679		$	77,797		$	45,930		$	(7,133	)	$	75,381		$	300,627

Profit margin		14	%		34	%		44	%		33	%		N/A			36	%		28	%

(1)	For the year ended December 31, 2009, LSV includes $105,471 of noncontrolling interest of the other partners of LSV.

A reconciliation of the total reported for the business segments to income from operations in the Consolidated Statements of Operations for the years ended December 31, 2011, 2010, and 2009 is as follows:


Year Ended December 31,	2011			2010			2009

Total operating profit from segments above	$	245,843		$	256,783		$	300,627

Corporate overhead expenses		(43,398	)		(40,715	)		(36,529	)
Noncontrolling interest reflected in segments		1,620			1,465			106,905
LSV Employee Group expenses (2)		0			0			(7,296	)


Income from operations	$	204,065		$	217,533		$	363,707

(2)	Includes $7,222 in 2009 of amortization expense related to intangible assets.

The following tables provide additional information for the years ended December 31, 2011, 2010, and 2009 pertaining to our business segments:


	Capital Expenditures						Depreciation
Year Ended December 31,	2011		2010		2009		2011		2010		2009

Private Banks	$	35,045	$	32,982	$	39,364	$	15,648	$	15,704	$	15,415
Investment Advisors		11,933		11,691		13,607		2,251		2,384		2,286
Institutional Investors		2,059		2,601		2,665		1,079		1,170		1,108
Investment Managers		3,081		3,659		4,306		1,809		1,891		1,580
Investments in New Businesses		577		608		831		114		148		176
LSV		0		0		1,358		0		0		395

Total from business segments	$	52,695	$	51,541	$	62,131	$	20,901	$	21,297	$	20,960

Corporate Overhead		530		799		1,085		570		605		571


	$	53,225	$	52,340	$	63,216	$	21,471	$	21,902	$	21,531


	Amortization
Year Ended December 31,	2011		2010		2009

Private Banks	$	18,081	$	15,100	$	24,058
Investment Advisors		6,201		5,467		8,550
Institutional Investors		864		1,213		927
Investment Managers		580		820		688
Investments in New Businesses		433		477		1,897
LSV		0		0		436

Total from business segments	$	26,159	$	23,077	$	36,556

LSV Employee Group		0		0		7,280
Corporate Overhead		1,129		971		772


	$	27,288	$	24,048	$	44,608


	Total Assets
	2011		2010

Private Banks	$	457,333	$	460,261
Investment Advisors		119,053		113,111
Institutional Investors		80,133		72,867
Investment Managers		95,760		96,378
Investments in New Businesses		5,962		6,801

Total from business segments	$	758,241	$	749,418

Corporate Overhead (3)		536,318		627,805


	$	1,294,559	$	1,377,223

(3)	Unallocated assets primarily consist of cash and cash equivalents, marketable securities, and certain other shared services assets.

The following table presents revenues based on the location of the use of the products or services:


For the Year Ended December 31,	2011		2010		2009

United States	$	785,506	$	767,068	$	950,891
International operations		144,221		133,767		109,657


	$	929,727	$	900,835	$	1,060,548

The following table presents assets based on their location:


	2011		2010

United States	$	1,098,643	$	1,193,775
International operations		195,916		183,448


	$	1,294,559	$	1,377,223

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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+ Details

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2011
Related Party Transactions [Abstract]
Related Party Transactions	Note 14 – Related Party Transactions: The Company, either by itself or through its wholly-owned subsidiaries, is a party to Investment Advisory and Administration Agreements with regulated investment companies (RICs) and other investment products which are administered by the Company. These investment products are offered to clients of the Company and its subsidiaries. Under the Investment Advisory and Administration Agreements, the Company receives a fee for providing investment advisory, administrative, and accounting services. The investment advisory and administration fee is a fixed percentage, referred to as basis points, of the average daily net assets, subject to certain limitations. Investment advisory and administration fees received by the Company totaled $364,602, $354,341 and $334,084 in 2011, 2010 and 2009, respectively. The Company is also a party to various agreements with several RICs which are advised and/or administered by the Company. The Company receives a fee for providing shareholder, administrative and distribution services pursuant to the provisions of various shareholder service, administrative service, and distribution plans adopted by the RICs. These fees totaled $39,017, $36,007 and $33,008 in 2011, 2010 and 2009, respectively. A portion of the transaction costs incurred by the RICs for securities transactions are directed to the Company's broker-dealer subsidiary in its capacity as an introducing broker-dealer. The Company recognized $2,772, $4,875 and $4,300 in commissions during 2011, 2010 and 2009, respectively.

- Definition

The entire disclosure for related party transactions, including the nature of the relationship(s), a description of the transactions, the amount of the transactions, the effects of any change in the method of establishing the terms of the transaction from the previous period, stated interest rate, expiration date, terms and manner of settlement per the agreement with the related party, and amounts due to or from related parties. If the entity and one or more other entities are under common ownership or management control and this control affects the operating results or financial position, disclosure includes the nature of the control relationship even if there are no transactions between the entities. Disclosure may also include the aggregate amount of current and deferred tax expense for each statement of earnings presented where the entity is a member of a group that files a consolidated tax return, the amount of any tax related balances due to or from affiliates as of the date of each statement of financial position presented, the principal provisions of the method by which the consolidated amount of current and deferred tax expense is allocated to the members of the group and the nature and effect of any changes in that method. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(k))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39691-107864

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39678-107864

+ Details

Quarterly Financial Data

12 Months Ended

Dec. 31, 2011

Quarterly Financial Data [Abstract]

Quarterly Financial Data

Note 15 – Quarterly Financial Data (Unaudited):


	For the Three Months Ended
2011	March 31			June 30			Sept. 30			Dec. 31

Revenues	$	232,493		$	237,760		$	233,227		$	226,247
Income before income taxes	$	92,164		$	82,820		$	74,900		$	68,603
Net income attributable to SEI	$	57,728		$	53,603		$	49,232		$	44,396
Basic earnings per share	$	.31		$	.29		$	.27		$	.25
Diluted earnings per share	$	.31		$	.29		$	.27		$	.25

Effective income tax rate		37.1	%		34.7	%		33.8	%		34.7	%

Total SIV-related gains (losses)	$	6,864		$	(1,944	)	$	(792	)	$	(738	)
Diluted earnings per share (1)	$	.02		$	.01		$	.00		$	.00

(1)	Attributable to SIV-related gains (losses).


	For the Three Months Ended
2010	March 31			June 30			Sept. 30			Dec. 31

Revenues	$	221,535		$	228,388		$	219,513		$	231,399
Income before income taxes	$	96,127		$	86,442		$	91,032		$	96,180
Net income attributable to SEI	$	59,420		$	53,478		$	56,389		$	62,400
Basic earnings per share	$	.31		$	.28		$	.30		$	.33
Diluted earnings per share	$	.31		$	.28		$	.30		$	.33

Effective income tax rate		37.9	%		37.8	%		37.8	%		37.0	%

Total SIV-related gains (losses)	$	17,349		$	3,913		$	8,728		$	14,257
Diluted earnings per share (2)	$	.06		$	.01		$	.03		$	.05

(2)	Attributable to SIV-related gains.

- Definition

The entire disclosure for the quarterly financial data in the annual financial statements. The disclosure may include a tabular presentation of financial information for each fiscal quarter for the current and previous year, including revenues, gross profit, income or loss before extraordinary items and earnings per share data. It also includes an indication if the information in the note is unaudited, comments on the aggregate effect of year-end adjustments, and an explanation of matters or transactions that affect comparability or are pertinent to an understanding of the information furnished.

+ References+ Details

Schedule II - Valuation And Qualifying Accounts And Reserves

12 Months Ended

Dec. 31, 2011

Valuation And Qualifying Accounts And Reserves [Abstract]

Schedule II - Valuation And Qualifying Accounts And Reserves

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES

FOR THE THREE YEARS ENDED DECEMBER 31, 2011, 2010, AND 2009


			Additions
Description	Balance at Beginning of Year		Charged to Costs and Expenses			Charged to Other Accounts		(Deductions)			Balance at End of Year

Allowance for doubtful accounts:

2011	$	1,195	$	0		$	0	$	(271	)	$	924
2010		3,348		0			0		(2,153	)		1,195
2009		2,656		692			0		0			3,348

Deferred income tax valuation allowance:

2011	$	9,008	$	(423	)	$	0	$	0		$	8,585
2010		6,217		1,443			1,348		0			9,008
2009		13,897		(32	)		0		(7,648	)		6,217

Summary Of Significant Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2011

Summary Of Significant Accounting Policies [Abstract]

Nature Of Operations

Nature of Operations

Principles Of Consolidation

Principles of Consolidation

Variable Interest Entities

Variable Interest Entities

Management's Use Of Estimates

Management's Use of Estimates

Revenue Recognition

Revenue Recognition

Cash And Cash Equivalents

Cash and Cash Equivalents

Restricted Cash

Restricted Cash

Allowances For Doubtful Accounts

Allowances for Doubtful Accounts

Concentration Of Credit Risk

Concentration of Credit Risk

Property And Equipment

Property and Equipment

Marketable Securities

Marketable Securities

Fair Value Of Financial Instruments

Fair Value of Financial Instruments

See Note 5 for information on related disclosures regarding fair value measurements

Capitalized Software

Capitalized Software

Income Taxes

Income Taxes

Foreign Currency Translation

Foreign Currency Translation

Earnings Per Common Share

Earnings Per Common Share


	For the Year ended December 31, 2011
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	204,959		182,547	$	1.12
Dilutive effect of stock options		0		1,580


Diluted earnings per common share	$	204,959		184,127	$	1.11


	For the Year ended December 31, 2010
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	231,687		188,468	$	1.23
Dilutive effect of stock options		0		1,853


Diluted earnings per common share	$	231,687		190,321	$	1.22


	For the Year ended December 31, 2009
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	174,335		190,821	$	0.91
Dilutive effect of stock options		0		962


Diluted earnings per common share	$	174,335		191,783	$	0.91

Stock-Based Compensation

Stock-Based Compensation

New Accounting Pronouncements

New Accounting Pronouncements

Reclassifications

Reclassifications

Certain prior year amounts have been reclassified to conform to current year presentation.

Summary Of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2011

Summary Of Significant Accounting Policies [Abstract]

Calculation Of Basic And Diluted Earnings Per Share


	For the Year ended December 31, 2011
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	204,959		182,547	$	1.12
Dilutive effect of stock options		0		1,580


Diluted earnings per common share	$	204,959		184,127	$	1.11


	For the Year ended December 31, 2010
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	231,687		188,468	$	1.23
Dilutive effect of stock options		0		1,853


Diluted earnings per common share	$	231,687		190,321	$	1.22


	For the Year ended December 31, 2009
	Net income attributable to SEI (Numerator)		Shares (Denominator)		Per-Share Amount

Basic earnings per common share	$	174,335		190,821	$	0.91
Dilutive effect of stock options		0		962


Diluted earnings per common share	$	174,335		191,783	$	0.91

Investment In Unconsolidated Affiliate (Tables)

12 Months Ended

Dec. 31, 2011

Investment In Unconsolidated Affiliate [Abstract]

Condensed Statement Of Operations Of LSV


Condensed Statement of Operations Year ended December 31,	2011		2010

Revenues	$	296,397	$	273,381

Net income	$	257,519	$	239,981

Condensed Balance Sheet Of LSV


Condensed Balance Sheet December 31,	2011		2010

Cash and cash equivalents	$	60,728	$	64,464
Accounts receivable, net of allowance for doubtful accounts of $804 and $369		75,269		75,056
Prepaid expenses and other current assets		604		848
Non-current assets		3,880		4,159


Total assets	$	140,481	$	144,527

Current liabilities	$	13,933	$	11,199
Partners' capital		126,548		133,328

Total liabilities and partners' capital	$	140,481	$	144,527

Unaudited Proforma Financial Information


Proforma Unaudited Condensed Statement of Operations Year ended December 31,	2009

Revenues	$	848,587
Expenses		(658,434	)


Income from operations		190,153

Other income, net		87
Equity in the earnings of unconsolidated affiliate		75,415


Net income before income taxes		265,655
Income taxes		89,886


Net income		175,769


Less: Net income attributable to the noncontrolling interest		(1,434	)


Net income attributable to SEI Investments	$	174,335

- Definition

Tabular disclosure of pro forma results of operations for a material business acquisition or series of individually immaterial business acquisitions that are material in the aggregate.

+ References+ Details

Composition Of Certain Financial Statement Captions (Tables)

12 Months Ended

Dec. 31, 2011

Composition Of Certain Financial Statement Captions [Abstract]

Receivables


	2011			2010
Trade receivables	$	37,822		$	34,528
Fees earned, not billed		92,916			93,506
Other receivables		12,295			9,651


		143,033			137,685

Less: Allowance for doubtful accounts		(924	)		(1,195	)


Receivables, net	$	142,109		$	136,490

Property And Equipment


	2011			2010

Buildings	$	136,949		$	135,935
Equipment		64,256			63,902
Land		9,929			9,890
Purchased software		77,971			74,720
Furniture and fixtures		17,999			18,566
Leasehold improvements		4,558			4,250
Construction in progress		339			121


		312,001			307,384

Less: Accumulated depreciation		(182,453	)		(166,816	)


Property and Equipment, net	$	129,548		$	140,568

Accrued Liabilities


	2011		2010

Accrued employee compensation	$	48,112	$	43,747
Accrued employee benefits and other personnel		5,408		6,988
Accrued consulting, outsourcing and professional fees		17,477		16,390
Accrued brokerage fees		8,665		11,942
Accrued sub-advisory, distribution and other asset management fees		17,091		16,778
Accrued income taxes		0		2,077
Accrued dividend payable		26,518		0
Other accrued liabilities		23,773		23,488


Accrued liabilities	$	147,044	$	121,410

- Definition

Tabular disclosure of the useful life and salvage value of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References+ Details

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Fair Value Of Certain Financial Assets And Liabilities


			At December 31, 2011
			Fair Value Measurements at Reporting Date Using
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)

Assets
Equity available-for-sale securities	$	8,010	$	8,010	$	0	$	0
Fixed-income available-for-sale securities		74,998		0		74,998		0
Fixed income securities owned		20,949		0		20,949		0
Trading securities		56,325		3,702		0		52,623


	$	160,282	$	11,712	$	95,947	$	52,623


			At December 31, 2010
			Fair Value Measurements at Reporting Date Using
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)

Assets
Equity available-for-sale securities	$	5,853	$	5,853	$	0	$	0
Fixed-income available-for-sale securities		68,917		0		68,917		0
Trading securities		104,594		3,949		0		100,645


	$	179,364	$	9,802	$	68,917	$	100,645

Reconciliation For All Assets And Liabilities Company Measured At Fair Value On Recurring Basis Using Significant Unobservable Inputs (Level 3)


	Trading Securities

Balance, January 1, 2010	$	120,714

Purchases		536
Issuances		0
Principal prepayments and settlements		(45,857	)
Sales		(18,995	)
Total gains or (losses) (realized/unrealized):
Included in earnings		44,247
Included in other comprehensive income		0
Transfers in and out of Level 3		0


Balance, December 31, 2010	$	100,645

Purchases		1,215
Issuances		0
Principal prepayments and settlements		(17,921	)
Sales		(34,706	)
Total gains or (losses) (realized/unrealized):
Included in earnings		3,390
Included in other comprehensive income		0
Transfers in and out of Level 3		0


Balance, December 31, 2011	$	52,623

- Definition

Tabular disclosure of the total amount of gains or losses for the period which are included in earnings or resulted in a change to net assets which gains or losses have arisen from the use of significant unobservable inputs (Level 3) to measure the fair value of assets and liabilities. Such gains or losses are attributable to the change in unrealized gains or losses relating to those assets and liabilities so valued which are still held at the reporting date and which change are also considered for disclosure; it may be expected that a description of where those unrealized gains or losses are reported in the statement of income or the statement of financial position would also be disclosed.

+ References+ Details

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2011

Marketable Securities [Abstract]

Investments Available For Sale


	For the Year ended December 31, 2011
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SEI-sponsored mutual funds	$	8,243	$	48	$	(360	)	$	7,931
Other mutual funds		69		10		0			79
Debt securities		70,604		4,394		0			74,998


	$	78,916	$	4,452	$	(360	)	$	83,008
	For the Year Ended December 31, 2010
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SEI-sponsored mutual funds	$	5,086	$	279	$	(14	)	$	5,351
Other mutual funds		443		59		0			502
Debt securities		67,118		1,799		0			68,917


	$	72,647	$	2,137	$	(14	)	$	74,770

Trading Securities


	For the Year ended December 31, 2011
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SIV securities	$	146,363	$	0	$	(94,955	)	$	51,408
LSV-sponsored mutual funds		2,049		1,653		0			3,702
Other investments		1,215		0		0			1,215


	$	149,627	$	1,653	$	(94,955	)	$	56,325
	For the Year ended December 31, 2010
	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value

SIV securities	$	231,026	$	0	$	(130,381	)	$	100,645
LSV-sponsored mutual funds		2,049		1,900		0			3,949


	$	233,075	$	1,900	$	(130,381	)	$	104,594

- Definition

Tabular disclosure of available-for-sale securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 03-1

-Paragraph 21

-Subparagraph a, b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 17

-Subparagraph a, b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19, 20, 21

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27337-111563

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27198-111563

Reference 6: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563

Reference 10: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

+ Details

Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2011

Shareholders' Equity [Abstract]

Assumptions Used In The Weighted Average Fair Value Of The Stock Options Granted


	2011			2010			2009

Expected term (in years)		7.65			7.45			7.49
Expected volatility		40.43	%		36.35	%		37.44	%
Expected dividend yield		1.90	%		0.84	%		1.02	%
Risk-free interest rate		1.66	%		3.01	%		3.31	%

Stock-Based Compensation Expense


	2011			2010			2009

Stock-based compensation expense	$	14,112		$	26,783		$	14,503
Less: Deferred tax benefit		(5,332	)		(10,068	)		(4,636	)


Stock-based compensation expense, net of tax	$	8,780		$	16,715		$	9,867

Schedule Of Recognition Of Compensation Cost


Period	Stock-Based Compensation Expense

2012	$	14,398
2013		12,704
2014		12,510
2015		3,846
2016		2,355
2017		2,310


	$	48,123

Stock Option Plans


	Number of Shares			Weighted Avg. Price

Balance as of December 31, 2008		28,883,000		$	19.90
Granted		4,222,000			17.66
Exercised		(2,055,000	)		10.53
Expired or canceled		(2,086,000	)		21.87


Balance as of December 31, 2009		28,964,000		$	20.09
Granted		2,883,000			23.84
Exercised		(1,633,000	)		16.04
Expired or canceled		(2,333,000	)		23.68


Balance as of December 31, 2010		27,881,000		$	20.42
Granted		2,534,000			15.77
Exercised		(1,364,000	)		16.37
Expired or canceled		(2,008,000	)		22.07


Balance as of December 31, 2011		27,043,000		$	20.06

Exercisable as of December 31, 2011		11,680,000		$	17.22

Available for future grant as of December 31, 2011		4,622,000

Stock Options Outstanding And Exercisable


	Options Outstanding at December 31, 2011						Options Exercisable at December 31, 2011
Range of Exercise Prices (Per Share)	Number of Shares		Weighted Average Exercise Price (Per Share)		Weighted Average Remaining Contractual Life (Years)		Number of Shares		Weighted Average Exercise Price (Per Share)		Weighted Average Remaining Contractual Life (Years)

$14.05 – 14.71		5,285,000	$	14.65		5.28		3,296,000	$	14.66		4.24
14.78 – 17.35		5,179,000		15.30		6.00		2,642,000		14.84		2.17
17.65 – 19.28		6,560,000		18.33		6.33		3,165,000		18.32		6.37
19.53 – 23.86		5,375,000		22.75		6.13		2,562,000		21.55		3.00
27.03 – 32.49		4,644,000		30.88		5.46		15,000		27.03		5.00


		27,043,000						11,680,000

Shares Repurchased And The Related Total Costs


Year	Total Number of Shares Repurchased		Total Cost

2011		11,109,000	$	211,165
2010		5,814,000		120,982
2009		3,198,000		54,114

Reconciliation Of Noncontrolling Interest On The Consolidated Statements Of Changes In Equity


Year Ended December 31,	2011			2010			2009

Noncontrolling interest
Beginning balance	$	15,155		$	121,895		$	109,722
Net income attributable to noncontrolling interest		1,691			1,633			98,097
Foreign currency translation adjustments		(703	)		685			1,797
Deconsolidation of LSV		0			(65,522	)		0
Deconsolidation of LSV Employee Group		0			(43,536	)		0
Distributions to noncontrolling interests		0			0			(87,337	)
Other		0			0			(384	)

Ending balance	$	16,143		$	15,155		$	121,895

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64, 65, A240

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 53

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 50

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6406099&loc=d3e25284-112666

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5444-113901

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Accumulated Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2011

Accumulated Comprehensive Income (Loss) [Abstract]

Accumulated Comprehensive Income (Loss)


	Foreign Currency Translation Adjustments			Unrealized Holding Gains (Losses) On Investments			Accumulated Other Comprehensive Income (Loss)
Total accumulated comprehensive loss at January 1, 2009	$	(9,787	)	$	(1,524	)	$	(11,311	)

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at January 1, 2009		3,148			0			3,148


Total accumulated comprehensive loss attributable to SEI Investments Company at January 1, 2009	$	(6,639	)	$	(1,524	)	$	(8,163	)

Total comprehensive income		8,734			2,484			11,218

Less: Total comprehensive income attributable to noncontrolling interest		(1,797	)		0			(1,797	)


Total comprehensive income attributable to SEI Investments Company	$	6,937		$	2,484		$	9,421

Total accumulated comprehensive income (loss) at December 31, 2009		(1,053	)		960			(93	)

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at December 31, 2009		1,351			0			1,351


Total accumulated comprehensive income attributable to SEI Investments Company at December 31, 2009	$	298		$	960		$	1,258

Total comprehensive income		2,205			379			2,584

Less: Total comprehensive income attributable to noncontrolling interest		(685	)		0			(685	)


Total comprehensive income attributable to SEI Investments Company	$	1,520		$	379		$	1,899

Total accumulated comprehensive income at December 31, 2010		1,152			1,339			2,491

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at December 31, 2010		666			0			666


Total accumulated comprehensive income attributable to SEI Investments Company at December 31, 2010	$	1,818		$	1,339		$	3,157
Total comprehensive loss		(3,195	)		1,235			(1,960	)

Less: Total comprehensive loss attributable to noncontrolling interest		703			0			703


Total comprehensive loss attributable to SEI Investments Company	$	(2,492	)	$	1,235		$	(1,257	)

Total accumulated comprehensive income at December 31, 2011		(2,043	)		2,574			531

Less: Total accumulated comprehensive loss attributable to noncontrolling interest at December 31, 2011		1,369			0			1,369


Total accumulated comprehensive income attributable to SEI Investments Company at December 31, 2011	$	(674	)	$	2,574		$	1,900

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2011

Income Taxes [Abstract]

Schedule Of Federal And State And Foreign Income Tax Provision


Year Ended December 31,	2011			2010		2009

Current
Federal	$	99,448		$	116,388	$	16,012
State		7,067			8,698		664
Foreign		4,603			3,365		5,412


		111,118			128,451		22,088

Deferred, including current deferred
Federal		(2,317	)		6,085		61,443
State		2,477			1,509		5,822
Foreign		6			0		0


		166			7,594		67,265


Income taxes attributable to the Noncontrolling interest (1)		553			416		533

Total income taxes	$	111,837		$	136,461	$	89,886

(1)	There is no income tax provision for LSV due to its partnership structure.

Components Of Net Income Before Income Taxes


Year Ended December 31,	2011		2010		2009

Domestic	$	309,391	$	360,937	$	255,390
Foreign		6,852		6,795		8,300


	$	316,243	$	367,732	$	263,690

Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate


Year Ended December 31,	2011			2010			2009

Statutory rate		35.0	%		35.0	%		35.0	%
State taxes, net of Federal tax benefit		2.0			2.0			1.5
Foreign tax expense and tax rate differential		0.6			0.4			1.1
Research and development tax credit		(0.7	)		(0.5	)		(0.8	)
Domestic Production Activities Deduction		(0.7	)		0			0
Domestic Production Activities Deduction, prior years, net		(1.5	)		0			0
Net change in uncertain tax positions(2)		0.4			0.2			(2.7	)
Other, net		0.1			(0.1	)		(0.2	)


		35.2	%		37.0	%		33.9	%

(2)

Schedule Of Deferred Income Tax Provision


Year Ended December 31,	2011			2010			2009

Difference in financial reporting and income tax depreciation methods	$	860		$	1,381		$	(86	)
Reserves not currently deductible		651			774			394
Reserves for Capital Support Agreements and basis difference in SIV securities		(3,336	)		4,822			60,491
Capitalized software currently deductible for tax purposes, net of amortization		5,157			5,734			2,876
State deferred income taxes		1,300			1,519			2,394
Revenue and expense recognized in different periods for financial reporting and income tax purposes		(1,188	)		(562	)		(122	)
Stock-based compensation expense		(3,101	)		(7,457	)		(4,386	)
Uncertain tax positions		(182	)		(106	)		2,861
Other, net		5			1,489			2,843


	$	166		$	7,594		$	67,265

Schedule Of Deferred Income Tax Liabilities


Year Ended December 31,	2011			2010

Current deferred income taxes:
Gross assets	$	1,151		$	1,388
Gross liabilities		(1	)		(1	)

		1,150			1,387
Valuation allowance		0			0

		1,150			1,387


Long-term deferred income taxes:
Gross assets		63,374			59,892
Gross liabilities		(148,540	)		(143,137	)

		(85,166	)		(83,245	)
Valuation allowance		(8,585	)		(9,008	)

		(93,751	)		(92,253	)


Net deferred income tax liability	$	(92,601	)	$	(90,866	)

Tax Effect Of Significant Temporary Differences Representing Deferred Tax Liabilities


Year Ended December 31,	2011			2010

Difference in financial reporting and income tax depreciation methods	$	(13,600	)	$	(11,402	)
Reserves not currently deductible		374			472
Capitalized software currently deductible for tax purposes, net of amortization		(139,455	)		(132,030	)
State deferred income taxes		6,717			5,337
Revenue and expense recognized in different periods for financial reporting and income tax purposes		3,149			3,015
Unrealized holding loss (gain) on investments		(927	)		(5,292	)
Stock-based compensation expense		43,879			40,096
State net operating loss carryforward		14,485			16,634
Valuation allowance on deferred tax assets		(8,585	)		(9,008	)
Federal benefit of state tax deduction for uncertain tax positions		1,725			1,542
Other, net		(363	)		(230	)


Net deferred income tax liability	$	(92,601	)	$	(90,866	)

Unrecognized Tax Benefit


	2011			2010			2009

Balance as of January 1	$	5,723		$	4,989		$	13,453

Tax positions related to current year:
Gross additions		2,392			1,372			1,905
Gross reductions		0			0			0

		2,392			1,372			1,905

Tax positions related to prior years:
Gross additions		1,992			0			0
Gross reductions		0			(104	)		0

		1,992			(104	)		0

Settlements		0			(102	)		(9,888	)
Lapses on statute of limitations		(697	)		(432	)		(481	)


Balance as of December 31	$	9,410		$	5,723		$	4,989

Business Segment Information (Tables)

12 Months Ended

Dec. 31, 2011

Business Segment Information [Abstract]

Financial Information About Business Segments

2011


	Private Banks			Investment Advisors			Institutional Investors			Investment Managers			Investments In New Businesses			Total

Revenues	$	348,122		$	189,780		$	210,027		$	177,975		$	3,823		$	929,727
Expenses		339,339			110,438			106,585			115,963			11,559			683,884

Operating profit (loss)	$	8,783		$	79,342		$	103,442		$	62,012		$	(7,736	)	$	245,843

Profit margin		3	%		42	%		49	%		35	%		N/A			26	%

2010


	Private Banks			Investment Advisors			Institutional Investors			Investment Managers			Investments In New Businesses			Total

Revenues	$	346,668		$	183,378		$	206,531		$	160,159		$	4,099		$	900,835
Expenses		310,633			110,388			106,934			103,421			12,676			644,052

Operating profit (loss)	$	36,035		$	72,990		$	99,597		$	56,738		$	(8,577	)	$	256,783

Profit margin		10	%		40	%		48	%		35	%		N/A			29	%

2009


	Private Banks			Investment Advisors			Institutional Investors			Investment Managers			Investments In New Businesses			LSV			Total

Revenues	$	361,273		$	166,097		$	177,721		$	139,004		$	4,492		$	211,961		$	1,060,548
Expenses (1)		309,300			109,418			99,924			93,074			11,625			136,580			759,921

Operating profit (loss)	$	51,973		$	56,679		$	77,797		$	45,930		$	(7,133	)	$	75,381		$	300,627

Profit margin		14	%		34	%		44	%		33	%		N/A			36	%		28	%

(1)	For the year ended December 31, 2009, LSV includes $105,471 of noncontrolling interest of the other partners of LSV.

Reconciliation Of Total Operating Profit Reported For Business Segments To Income From Operations In Consolidated Statements Of Operations


Year Ended December 31,	2011			2010			2009

Total operating profit from segments above	$	245,843		$	256,783		$	300,627

Corporate overhead expenses		(43,398	)		(40,715	)		(36,529	)
Noncontrolling interest reflected in segments		1,620			1,465			106,905
LSV Employee Group expenses (2)		0			0			(7,296	)


Income from operations	$	204,065		$	217,533		$	363,707

(2)	Includes $7,222 in 2009 of amortization expense related to intangible assets.

Additional Information Pertaining To Business Segments


	Capital Expenditures						Depreciation
Year Ended December 31,	2011		2010		2009		2011		2010		2009

Private Banks	$	35,045	$	32,982	$	39,364	$	15,648	$	15,704	$	15,415
Investment Advisors		11,933		11,691		13,607		2,251		2,384		2,286
Institutional Investors		2,059		2,601		2,665		1,079		1,170		1,108
Investment Managers		3,081		3,659		4,306		1,809		1,891		1,580
Investments in New Businesses		577		608		831		114		148		176
LSV		0		0		1,358		0		0		395

Total from business segments	$	52,695	$	51,541	$	62,131	$	20,901	$	21,297	$	20,960

Corporate Overhead		530		799		1,085		570		605		571


	$	53,225	$	52,340	$	63,216	$	21,471	$	21,902	$	21,531


	Amortization
Year Ended December 31,	2011		2010		2009

Private Banks	$	18,081	$	15,100	$	24,058
Investment Advisors		6,201		5,467		8,550
Institutional Investors		864		1,213		927
Investment Managers		580		820		688
Investments in New Businesses		433		477		1,897
LSV		0		0		436

Total from business segments	$	26,159	$	23,077	$	36,556

LSV Employee Group		0		0		7,280
Corporate Overhead		1,129		971		772


	$	27,288	$	24,048	$	44,608


	Total Assets
	2011		2010

Private Banks	$	457,333	$	460,261
Investment Advisors		119,053		113,111
Institutional Investors		80,133		72,867
Investment Managers		95,760		96,378
Investments in New Businesses		5,962		6,801

Total from business segments	$	758,241	$	749,418

Corporate Overhead (3)		536,318		627,805


	$	1,294,559	$	1,377,223

(3)	Unallocated assets primarily consist of cash and cash equivalents, marketable securities, and certain other shared services assets.

Revenues And Assets Based On The Location Of The Use Of The Products Or Services


For the Year Ended December 31,	2011		2010		2009

United States	$	785,506	$	767,068	$	950,891
International operations		144,221		133,767		109,657


	$	929,727	$	900,835	$	1,060,548

The following table presents assets based on their location:


	2011		2010

United States	$	1,098,643	$	1,193,775
International operations		195,916		183,448


	$	1,294,559	$	1,377,223

- Definition

Tabular disclosure of all significant reconciling items in the reconciliation of total profit or loss from reportable segments, to the entity's consolidated income before income taxes, extraordinary items, and discontinued operations.

+ References+ Details

- Definition

Tabular disclosure of each significant reconciling item, other than profit (loss), revenues, or assets, in the reconciliation of totals of such items in reportable segments to the entity's corresponding consolidated amount.

+ References+ Details

- Definition

Tabular disclosure of information concerning material long-lived assets (excluding financial instruments, customer relationships with financial institutions, mortgage and other servicing rights, deferred policy acquisition costs, and deferred taxes assets) located in identified geographic areas and/or the amount of revenue from external customers attributed to that country from which revenue is material. An entity may also provide subtotals of geographic information about groups of countries.

+ References+ Details

- Definition

Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

+ References+ Details

Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2011

Quarterly Financial Data [Abstract]

SIV-Related Gains (Losses)


	For the Three Months Ended
2011	March 31			June 30			Sept. 30			Dec. 31

Revenues	$	232,493		$	237,760		$	233,227		$	226,247
Income before income taxes	$	92,164		$	82,820		$	74,900		$	68,603
Net income attributable to SEI	$	57,728		$	53,603		$	49,232		$	44,396
Basic earnings per share	$	.31		$	.29		$	.27		$	.25
Diluted earnings per share	$	.31		$	.29		$	.27		$	.25

Effective income tax rate		37.1	%		34.7	%		33.8	%		34.7	%

Total SIV-related gains (losses)	$	6,864		$	(1,944	)	$	(792	)	$	(738	)
Diluted earnings per share (1)	$	.02		$	.01		$	.00		$	.00

(1)	Attributable to SIV-related gains (losses).


	For the Three Months Ended
2010	March 31			June 30			Sept. 30			Dec. 31

Revenues	$	221,535		$	228,388		$	219,513		$	231,399
Income before income taxes	$	96,127		$	86,442		$	91,032		$	96,180
Net income attributable to SEI	$	59,420		$	53,478		$	56,389		$	62,400
Basic earnings per share	$	.31		$	.28		$	.30		$	.33
Diluted earnings per share	$	.31		$	.28		$	.30		$	.33

Effective income tax rate		37.9	%		37.8	%		37.8	%		37.0	%

Total SIV-related gains (losses)	$	17,349		$	3,913		$	8,728		$	14,257
Diluted earnings per share (2)	$	.06		$	.01		$	.03		$	.05

(2)	Attributable to SIV-related gains.

Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009
Property, Plant and Equipment [Line Items]
Capitalized software, accumulated amortization	$ 117,100	$ 90,947
Capitalized software development costs for software sold to customers during period	40,954	38,729	43,944
Capitalized software, weighted average remaining life, years	10.5
Amortization expense related to capitalized software	26,153	23,053	35,894
Impairment charges for capitalized software development costs	0	0
Anti-dilutive employee stock options	15,914,000	13,181,000	22,997,000
Average exercise price of anti-dilutive employee stock options	$ 23.07	$ 23.79	$ 21.47
SEI Investments (Europe) Limited [Member]
Property, Plant and Equipment [Line Items]
Restricted cash	5,000	3,000
SEI Investments Distribution Co (SIDCO) [Member]
Property, Plant and Equipment [Line Items]
Restricted cash	1,000	1,000
Global Wealth Platform [Member]
Property, Plant and Equipment [Line Items]
Net book value of GWP	296,687
Capitalized software, accumulated amortization	87,762
Capitalized software development costs in-progress associated with future releases	11,552
Software development cost useful life, years	15
Capitalized software, weighted average remaining life, years	10.5
Accelerated amortization for GWP abandoned components			15,502
Net book value GWP components abandoned			15,502
SEI-Sponsored Open-Ended Money Market Mutual Funds [Member]
Property, Plant and Equipment [Line Items]
Investment in money market mutual funds at carrying value	$ 281,760	$ 383,946
Maximum [Member]
Property, Plant and Equipment [Line Items]
Software development cost useful life, years	15
Minimum [Member]
Property, Plant and Equipment [Line Items]
Software development cost useful life, years	3
Building And Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Useful life of property and equipment, minimum number of years	25
Useful life of property and equipment, maximum number of years	39
Equipment, Purchased Software And Furniture And Fixtures [Member]
Property, Plant and Equipment [Line Items]
Useful life of property and equipment, minimum number of years	3
Useful life of property and equipment, maximum number of years	5

Summary Of Significant Accounting Policies (Calculation Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Abstract]
Basic earnings per common share, Income (Numerator)	$ 44,396	$ 49,232	$ 53,603	$ 57,728	$ 62,400	$ 56,389	$ 53,478	$ 59,420	$ 204,959	$ 231,687	$ 174,335
Basic earnings per common share, Shares (Denominator)									182,547	188,468	190,821
Basic earnings per common share, Per Share Amount	$ 0.25	$ 0.27	$ 0.29	$ 0.31	$ 0.33	$ 0.30	$ 0.28	$ 0.31	$ 1.12	$ 1.23	$ 0.91
Dilutive effect of stock options, Income (Numerator)									0	0	0
Dilutive effect of stock options, Shares (Denominator)									1,580	1,853	962
Diluted earnings per common share, Income (Numerator)									$ 204,959	$ 231,687	$ 174,335
Diluted earnings per common share, Shares (Denominator)									184,127	190,321	191,783
Diluted earnings per common share, Per Share Amount	$ 0.25	$ 0.27	$ 0.29	$ 0.31	$ 0.33	$ 0.30	$ 0.28	$ 0.31	$ 1.11	$ 1.22	$ 0.91

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 07-4

-Paragraph 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

-Paragraph 36, 37, 38

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 20

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 7

-Paragraph 18

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 21

-Article 9

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.21)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6920599&loc=d3e1252-109256

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 55

-Paragraph 52

-URI http://asc.fasb.org/extlink&oid=6945512&loc=d3e4984-109258

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.23)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.19)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e565-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.22)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph A7

-Appendix A

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.18)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.19)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 87-21

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 10, 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28, 29, 30

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 19

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 20

-Article 9

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 14: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Net Income

-URI http://asc.fasb.org/extlink&oid=6518256

Reference 15: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Other Comprehensive Income

-URI http://asc.fasb.org/extlink&oid=6519514

Reference 16: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

+ Details

- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

+ References+ Details

- Definition

This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

-Paragraph 40

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

-Number 128

-Paragraph 10

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

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-Paragraph 13

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-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6920599&loc=d3e1448-109256

+ Details

Investment In Unconsolidated Affiliate (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended					12 Months Ended			1 Months Ended		12 Months Ended				1 Months Ended		12 Months Ended		1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 31, 2011	Dec. 31, 2006	Dec. 31, 2011 LSV [Member]	Dec. 31, 2010 LSV [Member]	Dec. 31, 2009 LSV [Member]	Jan. 31, 2011 LSV Employee Group [Member]	Jan. 31, 2010 LSV Employee Group [Member]	Dec. 31, 2011 LSV Employee Group [Member]	Dec. 31, 2010 LSV Employee Group [Member]	Dec. 31, 2009 LSV Employee Group [Member]	Dec. 31, 2006 LSV Employee Group [Member] years	Jan. 31, 2012 LSV Employee Group II [Member]	Apr. 30, 2011 LSV Employee Group II [Member]	Dec. 31, 2011 LSV Employee Group II [Member]	Dec. 31, 2010 LSV Employee Group II [Member]	Apr. 30, 2011 Bank of America [Member] LSV Employee Group II [Member]	Jan. 31, 2010 Maximum [Member] LSV [Member]
Investments in and Advances to Affiliates [Line Items]
Equity method investment, ownership percentage	41.00%				43.00%															50.00%
Total investment in LSV	$ 60,954	$ 64,409
Investment in LSV in excess of the underlying equity in net assets	3,717
Partnership distribution payments received from LSV						109,273	93,302	73,518		21,242
Purchase price related to intangible assets														72,220
Purchase price related to goodwill														19,780
Acquired intangible assets estimated useful life														10
Amortization expense of intangible assets													7,222
Principal amount of term loan														82,800	2,978			3,197
Maturity of term loan, years									January 2011
Credit agreement, expiration date									July 2012
Amount financed through new term loan																			3,655
Acquisition of additional partnership interest														8.00%
Purchase partnership interest																4,300
Debt instrument, periodic payment, principal											10,091	10,461			219		458
Current debt obligation				0
Goodwill						3,062
Maturity of term loan, years																	four
Interest Expense	$ 585	$ 1,478	$ 3,744										$ 1,510

Investment In Unconsolidated Affiliate (Condensed Statement Of Operations Of LSV) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investments in and Advances to Affiliates [Line Items]
Revenues	$ 226,247	$ 233,227	$ 237,760	$ 232,493	$ 231,399	$ 219,513	$ 228,388	$ 221,535	$ 929,727	$ 900,835	$ 1,060,548
Net income	44,396	49,232	53,603	57,728	62,400	56,389	53,478	59,420	204,959	231,687	174,335
Investment In Unconsolidated Affiliate [Member]
Investments in and Advances to Affiliates [Line Items]
Revenues									296,397	273,381
Net income									$ 257,519	$ 239,981

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Investment In Unconsolidated Affiliate (Condensed Balance Sheet Of LSV) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Investments in and Advances to Affiliates [Line Items]
Cash and cash equivalents	$ 420,986	$ 496,292	$ 590,877	$ 416,643
Accounts receivable, net of allowance for doubtful accounts of $804 and $369	142,109	136,490
Total Assets	1,294,559	1,377,223
Current liabilities	151,073	127,600
Total liabilities and partners' capital	1,294,559	1,377,223
Less: doubtful accounts	924	1,195
Investment In Unconsolidated Affiliate [Member]
Investments in and Advances to Affiliates [Line Items]
Cash and cash equivalents	60,728	64,464
Accounts receivable, net of allowance for doubtful accounts of $804 and $369	75,269	75,056
Prepaid expenses and other current assets	604	848
Non-current assets	3,880	4,159
Total Assets	140,481	144,527
Current liabilities	13,933	11,199
Partners' capital	126,548	133,328
Total liabilities and partners' capital	140,481	144,527
Less: doubtful accounts	$ 804	$ 369

Investments In Unconsolidated Affiliate (Unaudited Proforma Financial Information) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2009
Investment In Unconsolidated Affiliate [Abstract]
Revenues	$ 848,587
Expenses	(658,434)
Income from operations	190,153
Other income, net	87
Equity in the earnings of unconsolidated affiliate	75,415
Net income before income taxes	265,655
Income taxes	89,886
Net income	175,769
Less: Net income attributable to the noncontrolling interest	(1,434)
Net income attributable to SEI Investments	$ 174,335

Composition Of Certain Financial Statement Captions (Receivables) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Composition Of Certain Financial Statement Captions [Abstract]
Trade receivables	$ 37,822	$ 34,528
Fees earned, not billed	92,916	93,506
Other receivables	12,295	9,651
Gross receivables	143,033	137,685
Less: Allowance for doubtful accounts	(924)	(1,195)
Receivables, net	$ 142,109	$ 136,490

Composition Of Certain Financial Statement Captions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Composition Of Certain Financial Statement Captions [Abstract]
Buildings	$ 136,949	$ 135,935
Equipment	64,256	63,902
Land	9,929	9,890
Purchased software	77,971	74,720
Furniture and fixtures	17,999	18,566
Leasehold improvements	4,558	4,250
Construction in progress	339	121
Property and Equipment, gross	312,001	307,384
Less: Accumulated depreciation	(182,453)	(166,816)
Property and Equipment, net	129,548	140,568
Depreciation expense	21,471	21,902	21,531
Amortization expense for certain other assets	1,135	995	1,055
Gain on sale of private investment		$ 3,072

Composition Of Certain Financial Statement Captions (Accrued Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Composition Of Certain Financial Statement Captions [Abstract]
Accrued employee compensation	$ 48,112	$ 43,747
Accrued employee benefits and other personnel	5,408	6,988
Accrued consulting, outsourcing and professional fees	17,477	16,390
Accrued brokerage fees	8,665	11,942
Accrued sub-advisory, distribution and other asset management fees	17,091	16,778
Accrued income taxes	0	2,077
Accrued dividend payable	26,518	0
Other accrued liabilities	23,773	23,488
Accrued liabilities	$ 147,044	$ 121,410

Fair Value Measurements (Narrative) (Details) (Significant Unobservable Inputs (Level 3) [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities	$ 0	$ 0
Transfers of financial assets between levels within the fair value hierarchy	$ 0	$ 0

Fair Value Measurements (Fair Value Of Certain Financial Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity available-for-sale securities	$ 8,010	$ 5,853
Fixed-income available-for-sale securities	74,998	68,917
Fixed income securities owned	20,949	0
Trading securities	56,325	104,594
Assets, fair value	160,282	179,364
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity available-for-sale securities	8,010	5,853
Fixed-income available-for-sale securities	0	0
Fixed income securities owned	0
Trading securities	3,702	3,949
Assets, fair value	11,712	9,802
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity available-for-sale securities	0	0
Fixed-income available-for-sale securities	74,998	68,917
Fixed income securities owned	20,949
Trading securities	0	0
Assets, fair value	95,947	68,917
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity available-for-sale securities	0	0
Fixed-income available-for-sale securities	0	0
Fixed income securities owned	0
Trading securities	52,623	100,645
Assets, fair value	$ 52,623	$ 100,645

- Definition

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 320

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-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

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-Paragraph 2

-Subparagraph (b)-(g)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

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-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-Number 115

-Paragraph 12

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Number 115

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 86-40

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-Number 115

-Paragraph 3

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Paragraph 1

-Subparagraph (b)

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-Name Accounting Standards Codification

-Topic 942

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-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

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-Topic 320

-SubTopic 10

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-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

+ Details

- Definition

Total common and preferred stock (which is not mandatorily redeemable, redeemable at the option of the holder, or in any other way classified as liability) equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Number 115

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-Number 159

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-Name Implementation Guide (Q and A)

-Number FAS115

-Paragraph 35

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.4)

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-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),1(b))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Fair Value Measurements (Reconciliation For All Assets And Liabilities Company Measured At Fair Value On Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) (Trading Securities [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Trading Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 100,645	$ 120,714
Purchases	1,215	536
Issuances	0	0
Principal prepayments and settlements	(17,921)	(45,857)
Sales	(34,706)	(18,995)
Total gains or (losses) (realized/unrealized), included in earnings	3,390	44,247
Total gains or (losses) (realized/unrealized), included in other comprehensive income	0	0
Transfers in and out of Level 3	0	0
Ending balance	$ 52,623	$ 100,645

Marketable Securities (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010 securities	Dec. 31, 2009
Schedule of Available-for-sale Securities [Line Items]
Net unrealized holding gains	$ 2,574	$ 1,339
Unrealized holding gains during the period, income tax expense	1,518	784
Available-for-sale securities, gross realized gains	255	184	440
Available-for-sale securities, gross realized losses			123
Investments held, number of mutual funds			two
Net gain (loss) from investments	3,360	48,533	(4,926)
Number of SIV securities sold		3
Investment in LSV-sponsored funds, cost value	2,049
Investment in LSV-sponsored funds, fair value	3,702
Securities owned	20,949	0
SEI Private Trust Company [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt maturity, minimum	2020
Debt maturity, maximum	2041
U.S. Government Agency And Commercial Paper Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt maturity, maximum	one year
SIV Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Net gain from SIV securities	3,390	44,247
Gains from cash payments received from SIV securities	10,614	27,510
Gains or losses from increase/decrease in fair value of SIV securities	(7,224)	16,460
Three SIV securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cumulative losses from SIV securities		17,944
Net gain from SIV securities		277
Investments Impairment Charge [Member]
Schedule of Available-for-sale Securities [Line Items]
Net gain (loss) from investments			$ 901

Marketable Securities (Investments Available For Sale) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	$ 78,916	$ 72,647
Investment Available for Sale, Gross Unrealized Gains	4,452	2,137
Investment Available for Sale, Gross Unrealized Losses	(360)	(14)
Investment Available for Sale, Fair Value	83,008	74,770
SEI-Sponsored Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	8,243	5,086
Investment Available for Sale, Gross Unrealized Gains	48	279
Investment Available for Sale, Gross Unrealized Losses	(360)	(14)
Investment Available for Sale, Fair Value	7,931	5,351
Other Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	69	443
Investment Available for Sale, Gross Unrealized Gains	10	59
Investment Available for Sale, Gross Unrealized Losses	0	0
Investment Available for Sale, Fair Value	79	502
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	70,604	67,118
Investment Available for Sale, Gross Unrealized Gains	4,394	1,799
Investment Available for Sale, Gross Unrealized Losses	0	0
Investment Available for Sale, Fair Value	$ 74,998	$ 68,917

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details

- Definition

Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Marketable Securities (Trading Securities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Gain (Loss) on Investments [Line Items]
Trading Securities, Cost	$ 149,627	$ 233,075
Trading Securities, Gross Unrealized Gains	1,653	1,900
Trading Securities, Gross Unrealized Losses	(94,955)	(130,381)
Trading Securities, Fair Value	56,325	104,594
SIV Securities [Member]
Gain (Loss) on Investments [Line Items]
Trading Securities, Cost	146,363	231,026
Trading Securities, Gross Unrealized Gains	0	0
Trading Securities, Gross Unrealized Losses	(94,955)	(130,381)
Trading Securities, Fair Value	51,408	100,645
LSV-Sponsored Mutual Funds [Member]
Gain (Loss) on Investments [Line Items]
Trading Securities, Cost	2,049	2,049
Trading Securities, Gross Unrealized Gains	1,653	1,900
Trading Securities, Gross Unrealized Losses	0	0
Trading Securities, Fair Value	3,702	3,949
Other Investments [Member]
Gain (Loss) on Investments [Line Items]
Trading Securities, Cost	1,215
Trading Securities, Gross Unrealized Gains	0
Trading Securities, Gross Unrealized Losses	0
Trading Securities, Fair Value	$ 1,215

- Definition

The increase (decrease) resulting in a gain from the difference between the fair value and the carrying value, or in the comparative fair values, of trading securities held at each balance sheet date, that was included in earnings for the period.

+ References

+ Details

- Definition

The increase (decrease) resulting in a loss from the difference between the fair value and the carrying value, or in the comparative fair values, of trading securities held at each balance sheet date, that was included in earnings for the period.

+ References

+ Details

Lines Of Credit (Details) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2011 2012 Credit Facility [Member] USD ($)	Dec. 31, 2011 Canadian Subsidiary [Member] CAD
Line of Credit Facility [Line Items]
Credit agreement, years				five
Credit facility	$ 300,000			$ 300,000	2,000
Credit facility, expiration date	July 2012			February 2017
Credit facility, initiation date				February 2, 2012
Credit facility interest accrued, percentage above LIBOR	0.45%			1.25%
Credit facility, commitment fee per annum on daily unused portion, percent	0.09%			0.15%
Aggregate amount that may increase under credit facility				100,000
Credit facility, outstanding balance			254,000
Credit facility, principal payments	95,000	138,000	21,000
Credit facility, average interest rate	0.68%	0.77%	1.05%
Credit facility, interest charges and commitment fee	$ 585	$ 1,478	$ 2,491

Shareholders' Equity (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Sep. 30, 2010	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Jan. 31, 2012
Stock options vested in 2006, vesting period, years		seven
Weighted average fair value of stock options granted		$ 5.70	$ 9.65	$ 7.24
Change in management estimate of stock based compensation expense amortization			$ 11,663	$ 8,223
Previously recognized stock-based compensation costs reversed	6,375
Unrecognized compensation cost		48,123	27,460
Exercisable shares		11,680,000	14,247,000	11,801,000
Expiration dates for options outstanding, period start		December 10, 2012
Expiration dates for options outstanding, period end		December 13, 2021
Options outstanding weighted average remaining contractual life, years		5.9
Total intrinsic value of options exercised		8,642	9,961
Total intrinsic value of options outstanding		0
Aggregate intrinsic value of options exercisable		1,534
Common stock, market value		$ 17.35
Windfall tax benefits		142,872	141,438
Dividend distribution for rights agreement, date declared		December 2008
Dividend distribution for rights agreement, declared effective date		January 6, 2009
Rights received by common shareholder for each common share outstanding, rights		1
Series A Junior Participating Preferred stock, par value		$ 0.05	$ 0.05
Remaining stock repurchase authorization amount					95,823
Securities and assets of equivalent value, purchase price, per unit		$ 150
Number of days, rights become exercisable following public announcement		ten
Acquiring Person, beneficial ownership of the outstanding common stock, minimum percentage		20.00%
Holders, other than an acquiring person, right to purchase of common stock upon exercise of rights		twice
Common shares received by holders upon surrender of rights, percentage		50.00%
Rights non-voting, expiration date		Jan. 06, 2019
Rights non-voting, redeemable days		ten
Right redeemable price, per right		$ 0.01
Cash dividends		$ 48,558	$ 37,513	$ 32,422
2007 Plan [Member]
Number of active equity compensation plans		1
Options available for grant		20,000,000
Percentage of stock options vested when specified diluted earnings per share targets are achieved		50.00%
Remaining percentage of stock options vested when secondary, higher specified diluted earnings per share targets are achieved		50.00%
Employee Stock Purchase Plan [Member]
Employee stock purchase plan, employee eligible percentage on offerings of common stock		85.00%
Shares reserved under the plan		15,600,000
Issuance of common stock under the employee stock purchase plan, shares		11,474,000
Interim Cash Dividends [Member]
Cash dividends declared, per share		$ 0.12
Final Cash Dividends [Member]
Cash dividends declared, per share		$ 0.15

Shareholders' Equity (Assumptions Used In The Weighted Average Fair Value Of The Stock Options Granted) (Details)	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010 years	Dec. 31, 2009 years
Shareholders' Equity [Abstract]
Expected term (in years)	7.65	7.45	7.49
Expected volatility	40.43%	36.35%	37.44%
Expected dividend yield	1.90%	0.84%	1.02%
Risk-free interest rate	1.66%	3.01%	3.31%

- Definition

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

+ References+ Details

- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References+ Details

Shareholders' Equity (Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shareholders' Equity [Abstract]
Stock-based compensation expense	$ 14,112	$ 26,783	$ 14,503
Less: Deferred tax benefit	(5,332)	(10,068)	(4,636)
Stock-based compensation expense, net of tax	$ 8,780	$ 16,715	$ 9,867

- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References+ Details

Shareholders' Equity (Schedule Of Recognition Of Compensation Cost) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Temporary Equity [Line Items]
Stock-Based Compensation Expense	$ 48,123	$ 27,460
2012 [Member]
Temporary Equity [Line Items]
Stock-Based Compensation Expense	14,398
2013 [Member]
Temporary Equity [Line Items]
Stock-Based Compensation Expense	12,704
2014 [Member]
Temporary Equity [Line Items]
Stock-Based Compensation Expense	12,510
2015 [Member]
Temporary Equity [Line Items]
Stock-Based Compensation Expense	3,846
2016 [Member]
Temporary Equity [Line Items]
Stock-Based Compensation Expense	2,355
2017 [Member]
Temporary Equity [Line Items]
Stock-Based Compensation Expense	$ 2,310

Shareholders' Equity (Stock Option Plans) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance	27,043,000
Exercisable shares	11,680,000	14,247,000	11,801,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance	27,881,000	28,964,000	28,883,000
Balance, weighted avg. price	$ 20.42	$ 20.09	$ 19.90
Granted	2,534,000	2,883,000	4,222,000
Granted, weighted avg. price	$ 15.77	$ 23.84	$ 17.66
Exercised	(1,364,000)	(1,633,000)	(2,055,000)
Exercised, weighted avg. price	$ 16.37	$ 16.04	$ 10.53
Expired or canceled	(2,008,000)	(2,333,000)	(2,086,000)
Expired or canceled, weighted avg. price	$ 22.07	$ 23.68	$ 21.87
Balance	27,043,000	27,881,000	28,964,000
Balance, weighted avg. price	$ 20.06	$ 20.42	$ 20.09
Exercisable shares	11,680,000
Exercisable shares, weighted avg. price	$ 17.22
Available for future grant as of December 31, 2011	4,622,000

Shareholders' Equity (Stock Options Outstanding And Exercisable) (Details) (USD $)				12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 First Range Of Exercise Prices [Member] years	Dec. 31, 2011 Second Range Of Exercise Prices [Member] years	Dec. 31, 2011 Third Range Of Exercise Prices [Member] years	Dec. 31, 2011 Fourth Range Of Exercise Prices [Member] years	Dec. 31, 2011 Fifth Range Of Exercise Prices [Member] years
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares	27,043,000			5,285,000	5,179,000	6,560,000	5,375,000	4,644,000
Weighted Average Exercise Price (Per Share)				$ 14.65	$ 15.30	$ 18.33	$ 22.75	$ 30.88
Weighted Average Remaining Contractual Life (Years)	5.9			5.28	6.00	6.33	6.13	5.46
Number of Shares	11,680,000	14,247,000	11,801,000	3,296,000	2,642,000	3,165,000	2,562,000	15,000
Weighted Average Exercise Price (Per Share)				$ 14.66	$ 14.84	$ 18.32	$ 21.55	$ 27.03
Weighted Average Remaining Contractual Life (Years)				4.24	2.17	6.37	3.00	5.00
Lower range				$ 14.05	$ 14.78	$ 17.65	$ 19.53	$ 27.03
Upper range				$ 14.71	$ 17.35	$ 19.28	$ 23.86	$ 32.49

- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

+ References+ Details

Shareholders' Equity (Shares Repurchased And The Related Total Costs) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shareholders' Equity [Abstract]
Total Number of Shares Repurchased	11,109,000	5,814,000	3,198,000
Total Cost	$ 211,165	$ 120,982	$ 54,114

- Definition

Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

+ References+ Details

Shareholders' Equity (Reconciliation Of Noncontrolling Interest On The Consolidated Statements Of Changes In Equity) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Beginning balance	$ 15,155	$ 121,895	$ 109,722
Less: Net income attributable to noncontrolling interest	1,691	1,633	98,097
Foreign currency translation adjustments	(703)	685	1,797
Distributions to noncontrolling interests	0	0	(87,337)
Other	0	0	(384)
Ending balance	16,143	15,155	121,895
LSV [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Noncontrolling Interest, Decrease from Deconsolidation	0	(65,522)	0
LSV Employee Group [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Noncontrolling Interest, Decrease from Deconsolidation	$ 0	$ (43,536)	$ 0

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest).

+ References+ Details

- Definition

The portion of net Income or Loss attributable to the noncontrolling interest (if any) deducted in order to derive the portion attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph A1, A4, A5

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 55

-Paragraph 4K

-URI http://asc.fasb.org/extlink&oid=6922042&loc=SL4591552-111686

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6921930&loc=SL4573702-111684

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 55

-Paragraph 4J

-URI http://asc.fasb.org/extlink&oid=6922042&loc=SL4591551-111686

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Adjustment that results from the process of translating subsidiary financial statements and foreign equity investments into functional currency of the reporting entity, net of tax, attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 30

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 29

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 45

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6921628&loc=SL4569643-111683

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 45

-Paragraph 19

-URI http://asc.fasb.org/extlink&oid=6921628&loc=SL4569616-111683

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=6921930&loc=SL4573702-111684

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph c(3)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Accumulated Comprehensive Income (Loss) (Accumulated Comprehensive Income (Loss), Net Of Tax) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Accumulated other comprehensive income (loss), foreign currency translation adjustments	$ (674)	$ 1,818	$ 298	$ (6,639)
Accumulated other comprehensive income (loss), unrealized holding gains (losses) on investments	2,574	1,339	960	(1,524)
Accumulated other comprehensive income (loss)	1,900	3,157	1,258	(8,163)
Total comprehensive loss, foreign currency translation adjustments	(3,195)	2,205	8,734
Total comprehensive income (loss)	(1,960)	2,584	11,218
Total comprehensive loss, foreign currency translation adjustments, attributable to noncontrolling interest	(703)	685	1,797
Total comprehensive (loss) income, foreign currency translation adjustments, attributable to SEI Investments Company	(2,492)	1,520	6,937
Total comprehensive (loss) income, unrealized holding gains (losses) on investments, attributable to SEI Investments Company	1,235	379	2,484
Total comprehensive (loss) income, attributable to SEI Investments Company	(1,257)	1,899	9,421
SEI Investments Company [Member]
Accumulated other comprehensive income (loss), foreign currency translation adjustments	(2,043)	1,152	(1,053)	(9,787)
Accumulated other comprehensive income (loss), unrealized holding gains (losses) on investments	2,574	1,339	960	(1,524)
Accumulated other comprehensive income (loss)	531	2,491	(93)	(11,311)
Total comprehensive loss, foreign currency translation adjustments	(3,195)	2,205	8,734
Total comprehensive loss, unrealized holding gains (losses) on investments	1,235	379	2,484
Total comprehensive income (loss)	(1,960)	2,584	11,218
Noncontrolling Interest [Member]
Accumulated other comprehensive income (loss), foreign currency translation adjustments	1,369	666	1,351	3,148
Accumulated other comprehensive income (loss), unrealized holding gains (losses) on investments	0	0	0	0
Accumulated other comprehensive income (loss)	1,369	666	1,351	3,148
Total comprehensive loss, foreign currency translation adjustments, attributable to noncontrolling interest	703	(685)	(1,797)
Total comprehensive loss, unrealized holding gains (losses) on investments, attributable to noncontrolling interest	0	0	0
Total comprehensive loss, attributable to noncontrolling interest	$ 703	$ (685)	$ (1,797)

Commitments And Contingencies (Schedule Of Noncancellable Minimum Commitments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Commitments And Contingencies [Abstract]
Rent expense	$ 19,760	$ 17,210	$ 19,022
2012	17,892
2013	13,527
2014	6,997
2015	1,955
2016 and thereafter	10,419
Operating leases, future minimum payments due	$ 50,790

- Definition

The total of future contractually required payments on leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fourth year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the third year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the second year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due after the fifth year from the balance sheet date on leases defined as operating.

+ References+ Details

Income Taxes (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Undistributed earnings of foreign subsidiaries	$ 61,194
Capital loss carryforwards		4,256
Unrecognized tax benefit, excluding interest and penalties	9,410
Unrecognized tax benefits that would affect effective tax rate	8,320
Amount included in Current liabilities	1,768
Amount included in Other long-term liabilities	8,276	5,645
Amount of previously unrecognized tax benefits recognized	697
Tax related interest and penalties	634	690	864
Unrecognized tax benefits within the next 12 months	$ 1,768

Income Taxes (Schedule Of Federal And State And Foreign Income Tax Provision) (Details) (USD $)
In Thousands, unless otherwise specified

12 Months Ended

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Income Taxes [Abstract]

Federal, current

$ 99,448

$ 116,388

$ 16,012

State, current

7,067

8,698

664

Foreign, current

4,603

3,365

5,412

Current federal, state and foreign income tax

111,118

128,451

22,088

Federal, deferred

(2,317)

6,085

61,443

State, deferred

2,477

1,509

5,822

Foreign, deferred

Deferred income tax expense (benefit)

166

7,594

67,265

Income taxes attributable to the Noncontrolling interest

553

^[1]

416

^[1]

533

^[1]

Total income taxes

$ 111,837

$ 136,461

$ 89,886

[1]	There is no income tax provision for LSV due to its partnership structure.

Income Taxes (Components Of Net Income Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Domestic	$ 309,391	$ 360,937	$ 255,390
Foreign	6,852	6,795	8,300
Net Income Before Income	$ 316,243	$ 367,732	$ 263,690

Income Taxes (Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate) (Details)

3 Months Ended

12 Months Ended

Dec. 31, 2011

Sep. 30, 2011

Jun. 30, 2011

Mar. 31, 2011

Dec. 31, 2010

Sep. 30, 2010

Jun. 30, 2010

Mar. 31, 2010

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Income Taxes [Abstract]

Statutory rate

35.00%

State taxes, net of Federal tax benefit

2.00%

1.50%

Foreign tax expense and tax rate differential

0.60%

0.40%

1.10%

Research and development tax credit

(0.70%)

(0.50%)

(0.80%)

Domestic Production Activities Deduction

(0.70%)

0.00%

Domestic Production Activities Deduction, prior years, net

(1.50%)

0.00%

Net change in uncertain tax positions

0.40%

^[1]

0.20%

^[1]

(2.70%)

^[1]

Other, net

0.10%

(0.10%)

(0.20%)

Effective Income Tax Rate, Continuing Operations, Total

34.70%

33.80%

34.70%

37.10%

37.00%

37.80%

37.90%

35.20%

37.00%

33.90%

Uncertain tax positions, percentage of federal tax

0.25%

0.14%

0.50%

Uncertain tax positions, percentage of state tax

0.14%

0.06%

0.20%

Uncertain tax positions, percentage of foreign tax

0.01%

Uncertain tax positions, percentage of research and development tax credit settled with the internal revenue service

2.00%

[1]

Income Taxes (Schedule Of Deferred Income Tax Provision) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Difference in financial reporting and income tax depreciation methods	$ 860	$ 1,381	$ (86)
Reserves not currently deductible	651	774	394
Reserves for Capital Support Agreements and basis difference in SIV securities	(3,336)	4,822	60,491
Capitalized software currently deductible for tax purposes, net of amortization	5,157	5,734	2,876
State deferred income taxes	1,300	1,519	2,394
Revenue and expense recognized in different periods for financial reporting and income tax purposes	(1,188)	(562)	(122)
Stock-based compensation expense	(3,101)	(7,457)	(4,386)
Uncertain tax positions	(182)	(106)	2,861
Other, net	5	1,489	2,843
Deferred income tax expense (benefit)	$ 166	$ 7,594	$ 67,265

Income Taxes (Schedule Of Deferred Income Tax Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Gross assets	$ 1,151	$ 1,388
Gross liabilities	(1)	(1)
Current deferred income tax assets and liabilities	1,150	1,387
Valuation allowance	0	0
Current deferred income taxes	1,150	1,387
Gross assets	63,374	59,892
Gross liabilities	(148,540)	(143,137)
Long term deferred income tax assets and liabilities	(85,166)	(83,245)
Valuation allowance	(8,585)	(9,008)
Long term deferred income taxes	(93,751)	(92,253)
Net deferred income tax liability	$ (92,601)	$ (90,866)

Income Taxes (Tax Effect Of Significant Temporary Differences Representing Deferred Tax Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Difference in financial reporting and income tax depreciation methods	$ (13,600)	$ (11,402)
Reserves not currently deductible	374	472
Capitalized software currently deductible for tax purposes, net of amortization	(139,455)	(132,030)
State deferred income taxes	6,717	5,337
Revenue and expense recognized in different periods for financial reporting and income tax purpose	3,149	3,015
Unrealized holding loss (gain) on investments	(927)	(5,292)
Stock-based compensation expense	43,879	40,096
State net operating loss carryforward	14,485	16,634
Valuation allowance on deferred tax assets	(8,585)	(9,008)
Federal benefit of state tax deduction for uncertain tax positions	1,725	1,542
Other, net	(363)	(230)
Net deferred income tax liability	$ (92,601)	$ (90,866)

Income Taxes (Unrecognized Tax Benefit) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Unrecognized tax benefits, Beginning Balance	$ 5,723	$ 4,989	$ 13,453
Gross additions, current year	2,392	1,372	1,905
Gross reductions, current year	0	0	0
Tax positions related to current year	2,392	1,372	1,905
Gross additions, prior year	1,992	0	0
Gross reductions, prior year	0	(104)	0
Tax positions related to current year	1,992	(104)	0
Settlements	0	(102)	(9,888)
Lapses on statute of limitations	(697)	(432)	(481)
Unrecognized tax benefits, Ending Balance	$ 9,410	$ 5,723	$ 4,989

Business Segment Information (Financial Information About Business Segments) (Details) (USD $)
In Thousands, unless otherwise specified

3 Months Ended

12 Months Ended

Dec. 31, 2011

Sep. 30, 2011

Jun. 30, 2011

Mar. 31, 2011

Dec. 31, 2010

Sep. 30, 2010

Jun. 30, 2010

Mar. 31, 2010

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Segment Reporting Information [Line Items]

Revenues

$ 226,247

$ 233,227

$ 237,760

$ 232,493

$ 231,399

$ 219,513

$ 228,388

$ 221,535

$ 929,727

$ 900,835

$ 1,060,548

Expenses

683,884

644,052

759,921

^[1]

Operating profit (loss)

245,843

256,783

300,627

Profit margin

26.00%

29.00%

28.00%

Amount included in segment attributable to other partners

105,471

LSV [Member]

Segment Reporting Information [Line Items]

Revenues

211,961

Expenses

136,580

^[1]

Operating profit (loss)

75,381

Profit margin

36.00%

Private Banks [Member]

Segment Reporting Information [Line Items]

Revenues

348,122

346,668

361,273

Expenses

339,339

310,633

309,300

^[1]

Operating profit (loss)

8,783

36,035

51,973

Profit margin

3.00%

10.00%

14.00%

Investment Advisors [Member]

Segment Reporting Information [Line Items]

Revenues

189,780

183,378

166,097

Expenses

110,438

110,388

109,418

^[1]

Operating profit (loss)

79,342

72,990

56,679

Profit margin

42.00%

40.00%

34.00%

Institutional Investors [Member]

Segment Reporting Information [Line Items]

Revenues

210,027

206,531

177,721

Expenses

106,585

106,934

99,924

^[1]

Operating profit (loss)

103,442

99,597

77,797

Profit margin

49.00%

48.00%

44.00%

Investment Managers [Member]

Segment Reporting Information [Line Items]

Revenues

177,975

160,159

139,004

Expenses

115,963

103,421

93,074

^[1]

Operating profit (loss)

62,012

56,738

45,930

Profit margin

35.00%

33.00%

Investments In New Businesses [Member]

Segment Reporting Information [Line Items]

Revenues

3,823

4,099

4,492

Expenses

11,559

12,676

11,625

^[1]

Operating profit (loss)

$ (7,736)

$ (8,577)

$ (7,133)

Profit margin

0.00%

[1]	For the year ended December 31, 2009, LSV includes $105,471 of noncontrolling interest of the other partners of LSV.

Business Segment Information (Reconciliation Of Total Operating Profit Reported For Business Segments To Income From Operations In Consolidated Statements Of Operations) (Details) (USD $)
In Thousands, unless otherwise specified

12 Months Ended

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Segment Reporting Information [Line Items]

Total operating profit from segments above

$ 245,843

$ 256,783

$ 300,627

Corporate overhead expenses

(43,398)

(40,715)

(36,529)

Noncontrolling interest reflected in segments

1,620

1,465

106,905

Income from operations

204,065

217,533

363,707

LSV Employee Group [Member]

Segment Reporting Information [Line Items]

LSV Employee Group expenses

^[1]

(7,296)

^[1]

Amortization expense related to intangible assets

$ 7,222

[1]	Includes $7,222 in 2009 of amortization expense related to intangible assets.

- Definition

Amount of net income or loss for the period allocated to noncontrolling shareholders, unit holders, partners, or other equity holders in one or more of the entities consolidated into the reporting entity's financial statements other than those noncontrolling interests already defined within the taxonomy.

+ References+ Details

Business Segment Information (Additional Information Pertaining To Business Segments) (Details) (USD $)
In Thousands, unless otherwise specified

12 Months Ended

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Segment Reporting Information [Line Items]

Capital Expenditures

$ 53,225

$ 52,340

$ 63,216

Depreciation

21,471

21,902

21,531

Amortization

27,288

24,048

44,608

Total Assets

1,294,559

1,377,223

LSV [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

1,358

Depreciation

395

Amortization

436

LSV Employee Group [Member]

Segment Reporting Information [Line Items]

Amortization

7,280

Private Banks [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

35,045

32,982

39,364

Depreciation

15,648

15,704

15,415

Amortization

18,081

15,100

24,058

Total Assets

457,333

460,261

Investment Advisors [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

11,933

11,691

13,607

Depreciation

2,251

2,384

2,286

Amortization

6,201

5,467

8,550

Total Assets

119,053

113,111

Institutional Investors [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

2,059

2,601

2,665

Depreciation

1,079

1,170

1,108

Amortization

864

1,213

927

Total Assets

80,133

72,867

Investment Managers [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

3,081

3,659

4,306

Depreciation

1,809

1,891

1,580

Amortization

580

820

688

Total Assets

95,760

96,378

Investments In New Businesses [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

577

608

831

Depreciation

114

148

176

Amortization

433

477

1,897

Total Assets

5,962

6,801

Total From Business Segments [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

52,695

51,541

62,131

Depreciation

20,901

21,297

20,960

Amortization

26,159

23,077

36,556

Total Assets

758,241

749,418

Corporate Overhead [Member]

Segment Reporting Information [Line Items]

Capital Expenditures

530

799

1,085

Depreciation

570

605

571

Amortization

1,129

971

772

Total Assets

$ 536,318

^[1]

$ 627,805

^[1]

[1]	Unallocated assets primarily consist of cash and cash equivalents, marketable securities, and certain other shared services assets.

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References+ Details

- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References+ Details

Business Segment Information (Revenues And Assets Based On The Location Of The Use Of The Products Or Services) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 226,247	$ 233,227	$ 237,760	$ 232,493	$ 231,399	$ 219,513	$ 228,388	$ 221,535	$ 929,727	$ 900,835	$ 1,060,548
Assets	1,294,559				1,377,223				1,294,559	1,377,223
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									785,506	767,068	950,891
Assets	1,098,643				1,193,775				1,098,643	1,193,775
International Operations [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									144,221	133,767	109,657
Assets	$ 195,916				$ 183,448				$ 195,916	$ 183,448

- Definition

+ References+ Details

Related Party Transactions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Related Party Transactions [Abstract]
Investment advisory and administration fees received by the company	$ 364,602	$ 354,341	$ 334,084
Fees Received for providing shareholder, administrative and distribution services	39,017	36,007	33,008
Brokerage commissions revenue	$ 2,772	$ 4,875	$ 4,300

- Definition

The commission a broker-dealer charges when buying and selling securities on behalf of its customers. Acting as an agent, a broker-dealer may buy and sell securities on behalf of its customers. In return for such services, the broker-dealer charges a commission. Each time a customer enters into a buy or sell transaction, a commission is earned by the broker-dealer for its selling and administrative efforts. Commissions earned are usually related to the broker-dealer's customers' trading volume and the dollar amounts of the trades. In general, commissions are for smaller trades of exchange-listed stocks and bonds made by retail customers.

+ References+ Details

Quarterly Financial Data (SIV-Related Gains (Losses)) (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified

3 Months Ended

12 Months Ended

Dec. 31, 2011

Sep. 30, 2011

Jun. 30, 2011

Mar. 31, 2011

Dec. 31, 2010

Sep. 30, 2010

Jun. 30, 2010

Mar. 31, 2010

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Schedule of Available-for-sale Securities [Line Items]

Revenues

$ 226,247

$ 233,227

$ 237,760

$ 232,493

$ 231,399

$ 219,513

$ 228,388

$ 221,535

$ 929,727

$ 900,835

$ 1,060,548

Income before income taxes

68,603

74,900

82,820

92,164

96,180

91,032

86,442

96,127

318,487

369,781

362,318

Net income attributable to SEI

44,396

49,232

53,603

57,728

62,400

56,389

53,478

59,420

204,959

231,687

174,335

Basic earnings per share

$ 0.25

$ 0.27

$ 0.29

$ 0.31

$ 0.33

$ 0.30

$ 0.28

$ 0.31

$ 1.12

$ 1.23

$ 0.91

Diluted earnings per share

$ 0.25

$ 0.27

$ 0.29

$ 0.31

$ 0.33

$ 0.30

$ 0.28

$ 0.31

$ 1.11

$ 1.22

$ 0.91

Effective tax rates

34.70%

33.80%

34.70%

37.10%

37.00%

37.80%

37.90%

35.20%

37.00%

33.90%

SIV Securities [Member]

Schedule of Available-for-sale Securities [Line Items]

Diluted earnings per share

$ 0.00

^[1]

$ 0.00

^[1]

$ 0.01

^[1]

$ 0.02

^[1]

$ 0.05

^[2]

$ 0.03

^[2]

$ 0.01

^[2]

$ 0.06

^[2]

Total SIV-related gains (losses)

$ (738)

$ (792)

$ (1,944)

$ 6,864

$ 14,257

$ 8,728

$ 3,913

$ 17,349

[1]	Attributable to SIV-related gains (losses).
[2]	Attributable to SIV-related gains.

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

+ Details

- Definition

+ References+ Details

- Definition

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

+ References+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Schedule II - Valuation And Qualifying Accounts And Reserves (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance For Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 1,195	$ 3,348	$ 2,656
Additions, Charged to Costs and Expenses	0	0	692
Additions, Charged to Other Accounts	0	0	0
(Deductions)	(271)	(2,153)	0
Balance at End of Year	924	1,195	3,348
Deferred Income Tax Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	9,008	6,217	13,897
Additions, Charged to Costs and Expenses	(423)	1,443	(32)
Additions, Charged to Other Accounts	0	1,348	0
(Deductions)	0	0	(7,648)
Balance at End of Year	$ 8,585	$ 9,008	$ 6,217

Variable Interest Entities - Investment Products (Narrative) (Details)	12 Months Ended
	Dec. 31, 2011
Variable Interest Entities - Investment Products [Abstract]
Percentage not approached by expected return on any VIE investment	50.00%

Business Segment Information (Narrative) (Details)	12 Months Ended
Business Segment Information (Narrative) (Details)	Dec. 31, 2011	Dec. 31, 2010
Business Segment Information [Abstract]
Percentage of customers to total revenue	10.00%	10.00%