Property and Equipment, Net - Components of Company's Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 80,680	$ 92,540
Accumulated depreciation	(57,188)	(63,890)
Property and equipment, net	23,492	28,650
Office Furniture, Fixtures and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	14,816	17,740
Leaseholds and Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	40,320	47,269
Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 25,544	$ 27,531