Property and Equipment, Net - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 813,755	$ 809,371
Accumulated depreciation	(683,745)	(664,484)
Property and equipment, net	130,010	144,887
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, cost	170,816	171,515
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, cost	378,310	376,761
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, cost	102,992	102,424
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, cost	151,390	148,764
Other
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 10,247	$ 9,907