Income Taxes - Schedule of Components of Company's Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets Net Noncurrent Classification [Abstract]
Net operating loss	$ 32,551	$ 32,703
Accruals and reserves	2,934	2,887
Research and development credits	7,368	6,247
Stock-based compensation	4,622	5,028
Property and equipment and intangible assets	(1,855)	(2,036)
Other	2,842	2,802
Net deferred tax assets	48,462	47,631
Valuation allowance	(49,382)	(48,913)
Total noncurrent net deferred tax liabilities, net of valuation allowance	$ (920)	$ (1,282)