Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Apr. 11, 2016	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Purchase price of acquired company			$ 49,113	$ 1,671
Direct and incremental expenses		$ 74	2,616	$ 39
Goodwill		73,871	73,871		$ 46,776
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		100	2,600
Goodwill		$ 27,300	$ 27,300
Acquired identifiable intangible assets	$ 24,300
Acquired identifiable intangible assets, weighted average useful life			9 years 8 months 12 days
Fair value valuation of assets and liabilities, finalizing period			1 year
OpenSpan, Inc. | Maximum
Business Acquisition [Line Items]
Deposited in escrow period	18 months