Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred income tax assets:
Net operating loss carryforwards and credits	$ 16,090	$ 16,753
Acquired intangible assets	6,561	6,517
Reserves and accruals	2,209	2,115
Share-based compensation	2,837	3,092
Depreciation	395	397
Total deferred income tax assets	28,092	28,874
Deferred income tax liabilities:
Acquired intangible assets	(549)	(180)
Other	(312)	(162)
Total deferred income tax liabilities	(861)	(342)
Valuation allowance	(8,200)	(4,500)	$ (1,500)	$ (1,500)
Deferred income tax asset, net	$ 19,031	$ 24,032