Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 665,684	$ 695,008
Accumulated depreciation	(555,867)	(566,623)
Property and equipment, net	109,817	128,385	$ 125,176
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, cost	159,180	164,547
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, cost	250,585	291,681
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, cost	91,112	88,136
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 164,807	$ 150,644