Property and Equipment (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 725,162			$ 685,829
Less: Accumulated depreciation		(374,511)			(338,613)
Total property and equipment, net	[1]	350,651			347,216
Depreciation		37,100	$ 27,700
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross		532,371			493,536
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, gross		61,270			58,303
Leasehold and other improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross		84,429			74,721
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross		43,565			42,551
Building
Property, Plant and Equipment [Line Items]
Property and equipment, gross		0			6,551
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 3,527			$ 10,167
Accounting Standards Update 2016-02
Property, Plant and Equipment [Line Items]
Property and equipment, gross				$ (10,600)

[1] We adopted Topic 842 using the modified retrospective method as of January 1, 2019 and elected the transition option that allows us not to restate the comparative periods in our condensed consolidated financial statements in the year of adoption. See Note 2 for further details.