Property and Equipment, Net - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Computer hardware	$ 172,502	$ 162,346
Computer software	368,662	339,634
Furniture and equipment	100,219	96,536
Leasehold improvements	131,306	118,491
Other	10,188	9,560
Property and equipment, cost	782,877	726,567
Accumulated depreciation	(621,662)	(583,661)
Property and equipment, net	$ 161,215	$ 142,906