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Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Summary of Significant Accounting Policies [Line Items] |  |  |
Cash and cash equivalents | $ 839,891,000 | $ 834,697,000 |
Restricted cash | 302,000 | 301,000 |
Impairment charge on reclassified assets | 0 | 0 | $ 0
Capitalized software development costs | 24,340,000 | 33,958,000 | 35,293,000
Net book value of capitalized software | 236,023,000 | 239,783,000 |
Impairment charges related to capitalized software development costs | 0 | 5,250,000 | 0
Goodwill and intangible assets impairment | $ 0 | $ 0 | $ 0
Anti-dilutive employee stock options (in shares) | 9,530 | 11,388 | 12,439
Anti-dilutive employee stock options, average exercise price per share (in usd per share) | $ 61.83 | $ 61.32 | $ 60.35
Investment Managers |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Capitalized software development costs | $ 10,644,000 | $ 15,775,000 | $ 9,558,000
Capitalized software development costs in progress | 30,812,000 | 20,083,000 |
SEI Wealth Platform |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Capitalized software development costs | 13,696,000 | 18,183,000 | 25,735,000
Net book value of capitalized software | 204,621,000 |  |
Capitalized software development costs in progress | 4,300,000 |  |
Amortization expense related to the SEI Wealth Platform | $ 27,510,000 | 25,637,000 | 35,638,000
Weighted Average | SEI Wealth Platform |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of the SEI Wealth Platform | 8 years 2 months 12 days |  |
Buildings | Minimum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 25 years |  |
Buildings | Maximum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 39 years |  |
Building Improvements | Minimum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 5 years |  |
Building Improvements | Maximum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 15 years |  |
Computer Equipment | Minimum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 3 years |  |
Computer Equipment | Maximum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 5 years |  |
Purchased Software | Minimum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 3 years |  |
Purchased Software | Maximum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 5 years |  |
Furniture and fixtures | Minimum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 3 years |  |
Furniture and fixtures | Maximum |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Estimated useful life of property and equipment | 5 years |  |
SEI Sponsored Open Ended Money Market Mutual Funds |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Cash and cash equivalents | $ 341,311,000 | 397,838,000 |
SEI Investments Europe Limited |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Restricted cash | 250,000 | 250,000 |
SEI Investments Distribution Co |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Restricted cash | 52,000 | 51,000 |
SEI Sponsored Open Ended Money Market Mutual Funds |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |
Fees waived according to expense limitation agreements | $ 7,538,000 | $ 22,092,000 | $ 35,426,000

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