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Marketable Securities (Narrative) (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2022 | Mar. 31, 2021 | Dec. 31, 2021
Schedule of Investments [Line Items] |  |  |
Cash equivalents at fair value | $ 422,635,000 |  | $ 422,838,000
Net unrealized gains (loss) | (3,842,000) |  | (62,000)
Net unrealized gains (losses) income tax expense (benefit) | (1,148,000) |  | (18,000)
Available-for-sale securities, gross realized gains | 0 | $ 0 |
Mutual funds and equities, gross realized gains | 5,000 |  |
Mutual funds and equities, gross realized loss | 579,000 |  |
Other long-term investments | 52,778,000 |  | 107,918,000
Securities owned | 31,258,000 |  | 28,267,000
Available-for-sale debt securities |  |  |
Schedule of Investments [Line Items] |  |  |
Available-for-sale securities, gross realized losses | 246,000 | 327,000 |
Investment Funds Sponsored by LSV |  |  |
Schedule of Investments [Line Items] |  |  |
Other long-term investments | 7,270,000 |  | $ 6,916,000
Unrealized gains (losses) on investments | $ 354,000 | $ 457,000 |

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- Definition 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 Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e681-108580 + Details
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