Income Taxes - Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (15,785)	$ (8,982)	$ (9,052)
State taxes, net	4,840	(822)	(4,004)
Non-deductible stock compensation	1,085	(148)	(598)
Research credits	(814)	(320)	(280)
Change in valuation allowance	5,043	9,778	14,261
Other	(91)	$ 494	$ (327)
Income tax benefit	$ (5,722)