Property and Equipment, Net - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 656,463	$ 695,008
Accumulated depreciation	(538,768)	(566,623)
Property and equipment, net	117,695	128,385
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, cost	156,579	164,547
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, cost	247,164	291,681
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, cost	90,991	88,136
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 161,729	$ 150,644