Marketable Securities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Cash equivalents fair value	$ 450,240	$ 422,838
Net unrealized holding gain (loss)	(9,294)	(62)
Net unrealized holding gains (losses), income tax expense (benefit)	(2,777)	(18)
Equity securities, gross realized gains	263	741	$ 1,100
Equity securities, gross realized losses	773	72	250
Investment funds sponsored by LSV	104,673	107,918
Securities owned	32,148	28,267
Available for sale debt securities
Schedule of Investments [Line Items]
Available-for-sale securities, gross realized losses	602	1,160	902
Available-for-sale securities, gross realized gains	0	0	0
Investment funds sponsored by LSV
Schedule of Investments [Line Items]
Investment funds sponsored by LSV	6,366	6,916
Gains (losses) from the change in fair value of the funds	$ (550)	$ 750	$ 178

Accumulated Other Comprehensive Income (Loss), Debt Securities, Available For Sale Securities Adjustment Tax

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

+ References

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of realized gain 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 of realized loss 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 of realized gain from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of realized loss from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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Amount of long-term investments classified as other.

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Amount of realized gain (loss) on investment.

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