Income Taxes - Schedule of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 93,824	$ 90,921
Research and development tax credit carryforwards	9,979	8,646
Stock-based compensation	6,853	8,171
Deferred revenue	4,479	2,690
Other	2,807	2,471
Total deferred tax asset	117,942	112,899
Valuation allowance	$ (117,942)	(112,899)
Liabilities:
Net deferred tax liability related to intangible assets		(748)
Total deferred tax liability		$ (748)