Segment Information and Geographic Data - Revenues by Geographical Region (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 186,186	$ 173,621	$ 163,255	$ 151,798	$ 144,022	$ 131,826	$ 122,576	$ 114,556	$ 674,860	$ 512,980	$ 375,612
Americas [Member]
Segment Reporting Information [Line Items]
Total revenues									456,568	361,136	283,696
Europe [Member]
Segment Reporting Information [Line Items]
Total revenues									168,452	117,670	70,895
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Total revenues									$ 49,840	$ 34,174	$ 21,021
Revenue [Member] | Outside Of Americas [Member] | Geographic Concentration Risk [Member]
Segment Reporting Information [Line Items]
Percentage of revenues generated outside of the Americas									32.00%	30.00%	24.00%