Segment, Geographic and Product Information - Product Information Regarding Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Total revenues	$ 493,080	$ 435,756	$ 1,025,947	$ 942,220
Rates
Segment Reporting Information [Line Items]
Total revenues	144,209	137,129	308,946	295,938
Energy and Commodities
Segment Reporting Information [Line Items]
Total revenues	98,688	66,687	157,685	154,372
FX
Segment Reporting Information [Line Items]
Total revenues	77,527	74,347	155,355	145,165
Credit
Segment Reporting Information [Line Items]
Total revenues	65,806	61,257	188,347	149,082
Equities
Segment Reporting Information [Line Items]
Total revenues	57,373	58,291	125,487	125,419
Total brokerage revenues
Segment Reporting Information [Line Items]
Total revenues	443,603	397,711	935,820	869,976
All other revenues
Segment Reporting Information [Line Items]
Total revenues	$ 49,477	$ 38,045	$ 90,127	$ 72,244