Nature of Business and Financial Condition - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Net loss	$ (37,228)	$ (36,194)	$ (41,145)
Accumulated deficit	(376,720)	(339,492)
Cash and cash equivalents	$ 27,888	$ 17,031	$ 6,359	$ 24,625