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, 2026	Dec. 31, 2025
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 245,794	$ 519,734
Cash segregated for regulatory purposes	49,390	48,722
Total	419,721	675,851
Cash and Cash Equivalents [Member]
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	245,794	519,734
Cash Segregated under Federal Regulations [Member]
Cash And Cash Equivalents [Line Items]
Cash segregated for regulatory purposes	49,390	48,722
Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Cash And Cash Equivalents [Line Items]
Restricted cash deposits with clearing organizations and broker-dealers	122,677	107,223
Prepaid Expenses and Other Assets [Member]
Cash And Cash Equivalents [Line Items]
Other restricted cash deposits	$ 1,860	$ 172