Revenues from Contracts with Customers - Schedule of Revenues from Contracts with Customers and Other Sources of Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Revenues From Contracts With Customers [Line Items]
Total revenues from contracts with customers	$ 648,039	$ 434,971	$ 1,182,611	$ 888,584
Principal transactions	120,403	98,439	236,481	211,288
Interest and dividend income	15,268	17,145	26,897	26,909
Other revenues	294	206	2,255	2,594
Total revenues	784,004	550,761	1,448,244	1,129,375
Commissions
Revenues From Contracts With Customers [Line Items]
Total revenues from contracts with customers	599,496	395,081	1,094,207	810,253
Data, network and post-trade
Revenues From Contracts With Customers [Line Items]
Total revenues from contracts with customers	35,462	30,812	67,962	61,715
Fees from related parties
Revenues From Contracts With Customers [Line Items]
Total revenues from contracts with customers	5,241	4,643	9,663	9,064
Other revenues
Revenues From Contracts With Customers [Line Items]
Total revenues from contracts with customers	$ 7,840	$ 4,435	$ 10,779	$ 7,552