Computer Hardware and Other Property, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	$ 54,326		$ 54,326		$ 41,528
Accumulated depreciation	(30,708)		(30,708)		(23,486)
Total computer hardware and other property, net	23,618		23,618		18,042
Depreciation	2,918	$ 2,281	8,151	$ 6,463
Computer hardware
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	29,646		29,646		24,620
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	17,151		17,151		12,496
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	$ 7,529		$ 7,529		$ 4,412