Segment Information and Geographic Data - Reconciliation of Segment Gross Profit to Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Stock-based compensation expense	$ (9,528)	$ (9,034)	$ (28,087)	$ (25,151)
Gross profit	116,285	108,797	330,128	315,545
Cost of Revenue [Member]
Segment Reporting Information [Line Items]
Stock-based compensation expense	(785)	(780)	(2,357)	(1,894)
Material Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other items excluded from segment profit			(113)
Gross profit	116,285	108,797	330,128	315,545
Material Reconciling Items [Member] | Segment Profit [Member]
Segment Reporting Information [Line Items]
Segment gross profit	117,070	109,577	332,598	317,439
Material Reconciling Items [Member] | Cost of Revenue [Member]
Segment Reporting Information [Line Items]
Stock-based compensation expense	$ (785)	$ (780)	$ (2,357)	$ (1,894)