Business Segment and Geographic Information - Revenue by Client Sector (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Business Segment and Geographic Information
Gross revenues	$ 234,606	$ 186,792
Net revenue	234,606	186,792
Operating expenses	156,991	140,515
Operating income	77,615	46,277
Institutional
Business Segment and Geographic Information
Gross revenues	145,612	109,252
Wholesale
Business Segment and Geographic Information
Gross revenues	48,756	39,431
Retail
Business Segment and Geographic Information
Gross revenues	21,676	21,206
Market Data
Business Segment and Geographic Information
Gross revenues	$ 18,562	$ 16,903

Total costs of sales and operating expenses for the period.

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