Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets
Cash equivalents	$ 366,937	$ 207,101
Investment securities - fair value
Fair Value	78,143	39,990
Total assets measured at fair value	457,458	257,703
Sponsored funds
Investment securities - fair value
Fair Value	64,691	25,909
Equity securities
Investment securities - fair value
Fair Value	13,446	14,078
Debt securities
Investment securities - fair value
Fair Value	6	3
Nonqualified retirement plan assets
Investment securities - fair value
Nonqualified retirement plan assets	12,378	10,612
Level 1
Assets
Cash equivalents	366,937	207,101
Investment securities - fair value
Total assets measured at fair value	457,452	257,700
Level 1 \| Sponsored funds
Investment securities - fair value
Fair Value	64,691	25,909
Level 1 \| Equity securities
Investment securities - fair value
Fair Value	13,446	14,078
Level 1 \| Debt securities
Investment securities - fair value
Fair Value	0	0
Level 1 \| Nonqualified retirement plan assets
Investment securities - fair value
Nonqualified retirement plan assets	12,378	10,612
Level 2
Assets
Cash equivalents	0	0
Investment securities - fair value
Total assets measured at fair value	6	3
Level 2 \| Sponsored funds
Investment securities - fair value
Fair Value	0	0
Level 2 \| Equity securities
Investment securities - fair value
Fair Value	0	0
Level 2 \| Debt securities
Investment securities - fair value
Fair Value	6	3
Level 2 \| Nonqualified retirement plan assets
Investment securities - fair value
Nonqualified retirement plan assets	0	0
Level 3
Assets
Cash equivalents	0	0
Investment securities - fair value
Total assets measured at fair value	0	0
Level 3 \| Sponsored funds
Investment securities - fair value
Fair Value	0	0
Level 3 \| Equity securities
Investment securities - fair value
Fair Value	0	0
Level 3 \| Debt securities
Investment securities - fair value
Fair Value	0	0
Level 3 \| Nonqualified retirement plan assets
Investment securities - fair value
Nonqualified retirement plan assets	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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 investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Investments In Nonqualified Retirement Plan Assets

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