Investments and Other Marketable Securities - Investments Available For Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Available for sale debt securities, Cost	$ 154,211	$ 127,681
Available for sale debt securities, Fair Value	143,126	118,752
Available for sale and equity securities, Cost	192,794	163,409
Available for sale and equity securities, Gross Unrealized Gains	1,947	952
Available for sale and equity securities, Gross Unrealized (Losses)	(11,085)	(8,948)
Available for sale and equity securities, Fair Value	183,656	155,413
Available for sale debt securities
Debt Securities, Available-for-sale [Line Items]
Available for sale debt securities, Cost	154,211	127,681
Available for sale debt securities, Gross Unrealized Gains	0	0
Available for sale debt securities, Gross Unrealized (Losses)	(11,085)	(8,929)
Available for sale debt securities, Fair Value	143,126	118,752
SEI-sponsored investment products
Debt Securities, Available-for-sale [Line Items]
Equity securities, FV-NI, Cost	33,029	30,427
Equity securities, FV-NI, Gross Unrealized Gains	1,615	818
Equity securities, FV-NI, Gross Unrealized (Losses)	0	(19)
Equity securities, FV-NI, Fair Value	34,644	31,226
Equities and other investment products
Debt Securities, Available-for-sale [Line Items]
Equity securities, FV-NI, Cost	5,554	5,301
Equity securities, FV-NI, Gross Unrealized Gains	332	134
Equity securities, FV-NI, Gross Unrealized (Losses)	0	0
Equity securities, FV-NI, Fair Value	$ 5,886	$ 5,435

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Debt Securities, Available-For-Sale And Equity Securities, FV-NI, Accumulated Gross Unrealized Gain, Before Tax

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Equity Securities, FV-NI, Accumulated Gross Unrealized Gain, Before Tax

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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