Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 132,728	$ 86,910
Less accumulated depreciation	(49,079)	(34,442)
Property and equipment, net	83,649	52,468
Computer Equipment and Purchased Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	13,028	10,714
Employee Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	13,829	8,972
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	14,319	13,019
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	56,618	42,894
Equipment under Finance Lease [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	3,450	3,450
Internal Use Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	7,770	5,363
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 23,714	$ 2,498