Property and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 402,040		$ 402,040		$ 332,363
Less: Accumulated depreciation	(188,539)		(188,539)		(150,743)
Total property and equipment, net	213,501		213,501		181,620
Depreciation	22,200	$ 16,300	42,600	$ 30,800
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	272,883		272,883		222,648
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	39,781		39,781		32,132
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	39,836		39,836		37,095
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	34,746		34,746		31,574
Building
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,063		7,063		6,379
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,731		$ 7,731		$ 2,535