v2.4.0.6
Document and Entity Information
6 Months Ended
Jun. 30, 2010
Jul. 28, 2010
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2010  
Document Fiscal Year Focus 2010  
Document Fiscal Period Focus Q2  
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    188,488,789