Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands			1 Months Ended	12 Months Ended
	Dec. 31, 2016	Apr. 11, 2016	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Purchase price of acquired company				$ 49,113	$ 1,671	$ 3,918
Cash acquired from acquisition						2,100
Direct and incremental expenses				2,616	89	488
Goodwill	$ 73,164			73,164	46,776	46,860	$ 43,469
Purchase price of acquired company					1,100	$ 6,300
Additional Cash
Business Acquisition [Line Items]
Purchase price of acquired company				300	$ 500
Final Cash Payment | Subsequent Event
Business Acquisition [Line Items]
Purchase price of acquired company			$ 300
OpenSpan, Inc.
Business Acquisition [Line Items]
Purchase price of acquired company		$ 48,800
Cash acquired from acquisition		1,800
Escrow deposit	7,400
Direct and incremental expenses				2,600
Goodwill	$ 26,700			$ 26,700
Acquired identifiable intangible assets		$ 24,300
Acquired identifiable intangible assets, weighted average useful life				9 years 8 months 12 days
OpenSpan, Inc. | Maximum
Business Acquisition [Line Items]
Deposited in escrow period		18 months