Goodwill and Other Intangible Assets, Net - Acquisition-Related Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 206,156	$ 172,824
Accumulated Amortization	(165,639)	(147,394)
Net Book Value	40,517	25,430
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	176,768	150,826
Accumulated Amortization	(147,990)	(132,123)
Net Book Value	28,778	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
Noncompetition Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	7,390
Accumulated Amortization	(2,155)
Net Book Value	5,235
Acquired Lease Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	5,708	5,708
Accumulated Amortization	(5,324)	(5,208)
Net Book Value	$ 384	$ 500