Income Taxes - Details of Significant Components of Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 6,824	$ 20,627
State income taxes	1	1
Deferred revenue	2,505	4,723
Research and development and other credits	10,626	8,898
Reserves and accruals recognized in different periods	6,395	4,803
Basis difference in investment	967	968
Capitalized R&D expenses	4,654	1,576
Depreciation and amortization	523	783
Deferred rent	243	83
Other	14	(3)
Total deferred tax assets	32,752	42,459
Valuation allowance	(8,119)	(7,663)
Net deferred tax assets	$ 24,633	$ 34,796