Revenue from Contract with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 455,598	$ 529,845	$ 614,489
Total revenue	2,293,373	2,364,812	2,811,485
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	2,221,137	2,295,054	2,737,230
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	72,236	69,758	74,255
Commissions, net
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	326,660	398,270	474,710
Workflow technology
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	90,654	91,667	98,486
Analytics
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	38,284	39,908	41,293
Other sources of revenue
Disaggregation of Revenue [Line Items]
Other sources of revenue	1,837,775	1,834,967	2,196,996
Operating Segments | Market Making
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	29,571	42,180	40,955
Total revenue	1,843,523	1,812,839	2,203,046
Operating Segments | Market Making | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	1,843,523	1,812,839	2,203,046
Operating Segments | Market Making | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0
Operating Segments | Market Making | Commissions, net
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	29,571	42,180	40,955
Operating Segments | Market Making | Workflow technology
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Operating Segments | Market Making | Analytics
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Operating Segments | Market Making | Other sources of revenue
Disaggregation of Revenue [Line Items]
Other sources of revenue	1,813,952	1,770,659	2,162,091
Operating Segments | Execution Services
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	426,027	487,665	573,534
Total revenue	446,542	514,241	600,215
Operating Segments | Execution Services | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	374,306	444,483	525,960
Operating Segments | Execution Services | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	72,236	69,758	74,255
Operating Segments | Execution Services | Commissions, net
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	297,089	356,090	433,755
Operating Segments | Execution Services | Workflow technology
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	90,654	91,667	98,486
Operating Segments | Execution Services | Analytics
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	38,284	39,908	41,293
Operating Segments | Execution Services | Other sources of revenue
Disaggregation of Revenue [Line Items]
Other sources of revenue	20,515	26,576	26,681
Corporate
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Total revenue	3,308	37,732	8,224
Corporate | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	3,308	37,732	8,224
Corporate | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0
Corporate | Commissions, net
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Corporate | Workflow technology
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Corporate | Analytics
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Corporate | Other sources of revenue
Disaggregation of Revenue [Line Items]
Other sources of revenue	$ 3,308	$ 37,732	$ 8,224