Revenues from Contracts with Customers - Summary of Revenues from Contracts with Customers and Other Sources of Revenues (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	$ 1,406,692	$ 1,663,537	$ 1,690,290
Principal transactions	365,507	327,761	351,633
Interest and dividend income	21,007	21,977	12,332
Other revenues	2,096	2,089	2,506
Total revenues	1,795,302	2,015,364	2,056,761
Commissions
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	1,281,294	1,541,900	1,567,668
Data, software, and post-trade
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	96,389	89,963	81,920
Fees from related parties
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	14,734	14,856	25,754
Other revenues
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	14,275	16,818	14,948
Total revenues	$ 148,501	$ 145,703	$ 137,460