Property and Equipment, Net - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 672,296	$ 665,684
Accumulated depreciation	(573,928)	(555,867)
Property and equipment, net	98,368	109,817
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, cost	158,546	159,180
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, cost	253,399	250,585
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, cost	96,403	91,112
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 163,948	$ 164,807