Geographic Information and Business Segments - Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Total revenue	$ 692,985	$ 506,854	$ 1,335,824	$ 1,127,233
Income (loss) before income taxes and noncontrolling interest	155,385	35,467	295,205	170,231
Operating segments | Market Making
Segment Reporting Information [Line Items]
Total revenue	569,783	405,250	1,090,791	904,169
Income (loss) before income taxes and noncontrolling interest	144,542	43,741	271,495	167,850
Operating segments | Execution Services
Segment Reporting Information [Line Items]
Total revenue	127,059	109,116	244,847	227,593
Income (loss) before income taxes and noncontrolling interest	15,599	(115)	24,842	8,898
Segment reconciling items | Corporate
Segment Reporting Information [Line Items]
Total revenue	(3,857)	(7,512)	186	(4,529)
Income (loss) before income taxes and noncontrolling interest	$ (4,756)	$ (8,159)	$ (1,132)	$ (6,517)