Goodwill and Other Intangible Assets - Acquisition-Related Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 201,470	$ 172,824
Accumulated Amortization	(153,584)	(147,394)
Net Book Value	47,886	25,430
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	179,472	150,826
Accumulated Amortization	(138,167)	(132,123)
Net Book Value	41,305	18,703
Trademarks, Branding and Domain Names [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	16,290	16,290
Accumulated Amortization	(10,170)	(10,063)
Net Book Value	6,120	6,227
Acquired Lease Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	5,708	5,708
Accumulated Amortization	(5,247)	(5,208)
Net Book Value	$ 461	$ 500