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Cash and Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash and Cash Equivalents with Restricted or Segregated Cash (Detail) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Cash And Cash Equivalents [Line Items] |  |
Cash and cash equivalents | $ 473,299 | $ 544,478
Cash segregated for regulatory purposes | 48,351 | 47,107
Total | 642,774 | 700,459
Cash and Cash Equivalents [Member] |  |
Cash And Cash Equivalents [Line Items] |  |
Cash and cash equivalents | 473,299 | 544,478
Cash Segregated under Federal Regulations [Member] |  |
Cash And Cash Equivalents [Line Items] |  |
Cash segregated for regulatory purposes | 48,351 | 47,107
Receivables from Broker-Dealers, Clearing Organizations and Customers [Member] |  |
Cash And Cash Equivalents [Line Items] |  |
Restricted cash deposits with clearing organizations and broker-dealers | 119,942 | 107,652
Prepaid Expenses and Other Assets [Member] |  |
Cash And Cash Equivalents [Line Items] |  |
Other restricted cash deposits | $ 1,182 | $ 1,222

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- Definition Amount of cash and cash equivalent. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483467/210-10-45-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-4 + Details
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