v3.26.3
Shareholders' Equity - Earnings Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Accounting Policies [Abstract]        
Net income $ 171,247 $ 164,586 $ 547,574 $ 543,186
Less: Net income attributable to non-controlling interests 2,989 382 9,171 382
Net income attributable to SEI Investments Company $ 168,258 $ 164,204 $ 538,403 $ 542,804
Shares used to compute basic earnings per common share (in shares) 118,415 123,099 120,138 124,710
Dilutive effect of stock awards (in shares) 3,597 3,226 3,142 2,974
Shares used to compute diluted earnings per common share (in shares) 122,012 126,325 123,280 127,684
Basic earnings per common share (in USD per share) $ 1.42 $ 1.33 $ 4.48 $ 4.35
Diluted earnings per common share (in USD per share) $ 1.38 $ 1.30 $ 4.37 $ 4.25