Property and Equipment, Net - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 812,779	$ 809,371
Accumulated depreciation	(675,942)	(664,484)
Property and equipment, net	136,837	144,887
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, cost	171,447	171,515
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, cost	377,991	376,761
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, cost	102,919	102,424
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, cost	150,181	148,764
Other
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 10,241	$ 9,907