Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Computer hardware	$ 170,746	$ 162,346
Computer software	374,490	339,634
Furniture and equipment	100,472	96,536
Leasehold improvements	133,541	118,491
Other	9,993	9,560
Property and equipment, cost	789,242	726,567
Accumulated depreciation	(627,733)	(583,661)
Property and equipment, net	$ 161,509	$ 142,906	$ 121,754