Revenues from Contracts with Customers - Summary of Revenues from Contracts with Customers and Other Sources of Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers:	$ 384,638	$ 339,067	$ 795,459	$ 726,467
Principal transactions	94,883	88,169	209,812	203,770
Interest and dividend income	13,371	8,961	18,686	11,396
Other revenues (losses), net	188	(441)	1,990	587
Total revenues	493,080	435,756	1,025,947	942,220
Commissions
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers:	348,720	309,542	726,008	666,206
Data, network and post-trade
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers:	27,000	23,391	54,122	47,518
Fees from related parties
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers:	4,062	3,625	8,019	6,942
Other revenues
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers:	4,856	2,509	7,310	5,801
Total revenues	$ 49,477	$ 38,045	$ 90,127	$ 72,244