Goodwill and Other Intangible Assets - Acquisition-Related Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 198,562	$ 173,376
Accumulated Amortization	(126,065)	(106,515)
Net Book Value	72,497	66,861
Developed technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	176,562	151,376
Accumulated Amortization	(112,474)	(94,560)
Net Book Value	64,088	56,816
Trademarks, branding and domain names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	16,292	16,292
Accumulated Amortization	(8,938)	(7,861)
Net Book Value	7,354	8,431
Acquired lease intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	5,708	5,708
Accumulated Amortization	(4,653)	(4,094)
Net Book Value	$ 1,055	$ 1,614