Cash and Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash and Cash Equivalents with Restricted or Segregated Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 396,487	$ 430,746
Cash segregated under federal regulations	52,015	50,947
Deposits with clearing organizations and broker-dealers	108,719	88,923
Total	557,329	572,664
Cash and Cash Equivalents [Member]
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	396,487	430,746
Cash Segregated under Federal Regulations [Member]
Cash And Cash Equivalents [Line Items]
Cash segregated under federal regulations	52,015	50,947
Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Cash And Cash Equivalents [Line Items]
Deposits with clearing organizations and broker-dealers	108,719	88,923
Prepaid Expenses and Other Assets [Member]
Cash And Cash Equivalents [Line Items]
Other deposits	$ 108	$ 2,048