Goodwill and Other Intangible Assets - Acquisition-Related Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 203,147	$ 172,824
Accumulated Amortization	(159,251)	(147,394)
Net Book Value	43,896	25,430
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	181,149	150,826
Accumulated Amortization	(143,796)	(132,123)
Net Book Value	37,353	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	(5,285)	(5,208)
Net Book Value	$ 423	$ 500