Cash and Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash and Cash Equivalents with Restricted or Segregated Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 519,734	$ 544,478
Cash segregated for regulatory purposes	48,722	47,107
Total	675,851	700,459	$ 611,672
Cash and Cash Equivalents [Member]
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	519,734	544,478	451,280
Cash Segregated under Federal Regulations [Member]
Cash And Cash Equivalents [Line Items]
Cash segregated for regulatory purposes	48,722	47,107	45,122
Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Cash And Cash Equivalents [Line Items]
Restricted cash deposits with clearing organizations and broker-dealers	107,223	107,652	115,151
Prepaid Expenses and Other Assets [Member]
Cash And Cash Equivalents [Line Items]
Other restricted cash deposits	$ 172	$ 1,222	$ 119