Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred income tax assets:
Net operating loss carryforwards and credits	$ 16,753	$ 17,539
Acquired intangible assets	6,517	6,444
Reserves and accruals	2,115	1,565
Share-based compensation	3,092	2,877
Depreciation	397	407
Total deferred income tax assets	28,874	28,832
Deferred income tax liabilities:
Acquired intangible assets	(180)	(18)
Other	(162)	(144)
Total deferred income tax liabilities	(342)	(162)
Valuation allowance	(4,500)	(1,500)	$ (1,500)	$ (37,726)
Deferred income tax asset , net	$ 24,032	$ 27,170