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Fair value of obligations measured on a recurring basis.

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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, 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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Fair Value Measurements - Financial Assets and Liabilities Measured on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024
Assets
Restricted cash	$ 116,675	$ 119,724	$ 109,618
Securities owned — trading	124,639	42,267
Fair Value, Recurring
Assets
Restricted cash	111,713	100,368
Securities owned — trading	124,639	42,267
Other assets	1,272,201	1,139,515
Total assets at fair value	2,958,448	2,007,986
Other liabilities:
Securities sold, but not yet purchased	210	169
Total other liabilities	438,458	475,750
Total liabilities at fair value	438,458	475,750
Fair Value, Recurring \| Level 1
Assets
Restricted cash	111,713	100,368
Securities owned — trading	124,610	42,256
Other assets	1,269,888	1,135,526
Total assets at fair value	2,956,106	2,003,986
Other liabilities:
Securities sold, but not yet purchased	198	151
Total other liabilities	313,597	278,834
Total liabilities at fair value	313,597	278,834
Fair Value, Recurring \| Level 2
Assets
Restricted cash	0	0
Securities owned — trading	29	11
Other assets	2,313	3,989
Total assets at fair value	2,342	4,000
Other liabilities:
Securities sold, but not yet purchased	12	18
Total other liabilities	12	18
Total liabilities at fair value	12	18
Fair Value, Recurring \| Level 3
Assets
Restricted cash	0	0
Securities owned — trading	0	0
Other assets	0	0
Total assets at fair value	0	0
Other liabilities:
Securities sold, but not yet purchased	0	0
Total other liabilities	124,849	196,898
Total liabilities at fair value	124,849	196,898
Equity securities \| Fair Value, Recurring
Other liabilities:
Securities sold, but not yet purchased	181	151
Equity securities \| Fair Value, Recurring \| Level 1
Other liabilities:
Securities sold, but not yet purchased	181	151
Equity securities \| Fair Value, Recurring \| Level 2
Other liabilities:
Securities sold, but not yet purchased	0	0
Equity securities \| Fair Value, Recurring \| Level 3
Other liabilities:
Securities sold, but not yet purchased	0	0
Mutual funds \| Fair Value, Recurring
Other liabilities:
Securities sold, but not yet purchased	17
Mutual funds \| Fair Value, Recurring \| Level 1
Other liabilities:
Securities sold, but not yet purchased	17
Mutual funds \| Fair Value, Recurring \| Level 2
Other liabilities:
Securities sold, but not yet purchased	0
Mutual funds \| Fair Value, Recurring \| Level 3
Other liabilities:
Securities sold, but not yet purchased	0
Debt Securities \| Fair Value, Recurring
Other liabilities:
Securities sold, but not yet purchased	12	18
Debt Securities \| Fair Value, Recurring \| Level 1
Other liabilities:
Securities sold, but not yet purchased	0	0
Debt Securities \| Fair Value, Recurring \| Level 2
Other liabilities:
Securities sold, but not yet purchased	12	18
Debt Securities \| Fair Value, Recurring \| Level 3
Other liabilities:
Securities sold, but not yet purchased	0	0
Cash equivalents \| Fair Value, Recurring
Assets
Cash equivalents	802,440	53,672
Cash equivalents \| Fair Value, Recurring \| Level 1
Assets
Cash equivalents	802,440	53,672
Cash equivalents \| Fair Value, Recurring \| Level 2
Assets
Cash equivalents	0	0
Cash equivalents \| Fair Value, Recurring \| Level 3
Assets
Cash equivalents	0	0
Cash equivalents segregated under federal or other regulations \| Fair Value, Recurring
Assets
Cash equivalents	647,455
Cash equivalents segregated under federal or other regulations \| Fair Value, Recurring \| Federal Or Other Regulations
Assets
Cash equivalents		672,164
Cash equivalents segregated under federal or other regulations \| Fair Value, Recurring \| Level 1 \| Federal Or Other Regulations
Assets
Cash equivalents	647,455	672,164
Cash equivalents segregated under federal or other regulations \| Fair Value, Recurring \| Level 2 \| Federal Or Other Regulations
Assets
Cash equivalents	0	0
Cash equivalents segregated under federal or other regulations \| Fair Value, Recurring \| Level 3 \| Federal Or Other Regulations
Assets
Cash equivalents	0	0
U.S. treasury obligations
Assets
Securities owned — trading	109,419	28,511
U.S. treasury obligations \| Fair Value, Recurring
Assets
Securities owned — trading	109,419	28,511
U.S. treasury obligations \| Fair Value, Recurring \| Level 1
Assets
Securities owned — trading	109,419	28,511
U.S. treasury obligations \| Fair Value, Recurring \| Level 2
Assets
Securities owned — trading	0	0
U.S. treasury obligations \| Fair Value, Recurring \| Level 3
Assets
Securities owned — trading	0	0
Mutual funds \| Fair Value, Recurring
Assets
Securities owned — trading	14,900	13,627
Mutual funds \| Fair Value, Recurring \| Level 1
Assets
Securities owned — trading	14,900	13,627
Mutual funds \| Fair Value, Recurring \| Level 2
Assets
Securities owned — trading	0	0
Mutual funds \| Fair Value, Recurring \| Level 3
Assets
Securities owned — trading	0	0
Money market funds
Assets
Securities owned — trading	123	110
Money market funds \| Fair Value, Recurring
Assets
Securities owned — trading	123	110
Money market funds \| Fair Value, Recurring \| Level 1
Assets
Securities owned — trading	123	110
Money market funds \| Fair Value, Recurring \| Level 2
Assets
Securities owned — trading	0	0
Money market funds \| Fair Value, Recurring \| Level 3
Assets
Securities owned — trading	0	0
Equity securities
Assets
Securities owned — trading	168	8
Equity securities \| Fair Value, Recurring
Assets
Securities owned — trading	168	8
Equity securities \| Fair Value, Recurring \| Level 1
Assets
Securities owned — trading	168	8
Equity securities \| Fair Value, Recurring \| Level 2
Assets
Securities owned — trading	0	0
Equity securities \| Fair Value, Recurring \| Level 3
Assets
Securities owned — trading	0	0
Debt securities
Assets
Securities owned — trading	29	11
Debt securities \| Fair Value, Recurring
Assets
Securities owned — trading	29	11
Debt securities \| Fair Value, Recurring \| Level 1
Assets
Securities owned — trading	0	0
Debt securities \| Fair Value, Recurring \| Level 2
Assets
Securities owned — trading	29	11
Debt securities \| Fair Value, Recurring \| Level 3
Assets
Securities owned — trading	0	0
Deferred compensation plan \| Fair Value, Recurring
Assets
Other assets	956,489	856,843
Deferred compensation plan \| Fair Value, Recurring \| Level 1
Assets
Other assets	956,489	856,843
Deferred compensation plan \| Fair Value, Recurring \| Level 2
Assets
Other assets	0	0
Deferred compensation plan \| Fair Value, Recurring \| Level 3
Assets
Other assets	0	0
Fractional shares — investment \| Fair Value, Recurring
Assets
Other assets	313,399	278,683
Other liabilities:
Obligations	313,399	278,683
Fractional shares — investment \| Fair Value, Recurring \| Level 1
Assets
Other assets	313,399	278,683
Other liabilities:
Obligations	313,399	278,683
Fractional shares — investment \| Fair Value, Recurring \| Level 2
Assets
Other assets	0	0
Other liabilities:
Obligations	0	0
Fractional shares — investment \| Fair Value, Recurring \| Level 3
Assets
Other assets	0	0
Other liabilities:
Obligations	0	0
Other investments \| Fair Value, Recurring
Assets
Other assets	2,313	3,989
Other investments \| Fair Value, Recurring \| Level 1
Assets
Other assets	0	0
Other investments \| Fair Value, Recurring \| Level 2
Assets
Other assets	2,313	3,989
Other investments \| Fair Value, Recurring \| Level 3
Assets
Other assets	0	0
Contingent consideration \| Fair Value, Recurring
Other liabilities:
Obligations	124,849	196,898
Contingent consideration \| Fair Value, Recurring \| Level 1
Other liabilities:
Obligations	0	0
Contingent consideration \| Fair Value, Recurring \| Level 2
Other liabilities:
Obligations	0	0
Contingent consideration \| Fair Value, Recurring \| Level 3
Other liabilities:
Obligations	$ 124,849	$ 196,898