Cash and Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash and Cash Equivalents with Restricted or Segregated Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 486,224	$ 544,478
Cash segregated for regulatory purposes	47,514	47,107
Total	644,454	700,459
Cash and Cash Equivalents [Member]
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	486,224	544,478
Cash Segregated under Federal Regulations [Member]
Cash And Cash Equivalents [Line Items]
Cash segregated for regulatory purposes	47,514	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	110,544	107,652
Prepaid Expenses and Other Assets [Member]
Cash And Cash Equivalents [Line Items]
Other cash deposits	$ 172	$ 1,222