Segment, Geographic and Product Information - Product Information Regarding Revenues (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Total revenues	$ 2,025,401	$ 1,795,302	$ 2,015,364
Total brokerage revenues
Segment Reporting Information [Line Items]
Total revenues	1,832,624	1,646,801	1,869,661
Rates
Segment Reporting Information [Line Items]
Total revenues	610,451	549,503	558,507
Energy and Commodities
Segment Reporting Information [Line Items]
Total revenues	386,206	291,665	296,458
FX
Segment Reporting Information [Line Items]
Total revenues	314,706	299,721	301,328
Credit
Segment Reporting Information [Line Items]
Total revenues	284,744	271,419	287,608
Equities
Segment Reporting Information [Line Items]
Total revenues	236,517	234,493	247,673
Insurance1
Segment Reporting Information [Line Items]
Total revenues	0	0	178,087
All other revenues
Segment Reporting Information [Line Items]
Total revenues	$ 192,777	$ 148,501	$ 145,703