Nature of Business, Financial Condition and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 15, 2015 $ / shares	Sep. 30, 2016 USD ($) $ / shares	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) $ / shares	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)
Accounting Policies [Abstract]
Net loss		$ (9,849)	$ (6,519)	$ (34,939)	$ (28,232)
Deficit accumulated		(374,431)		(374,431)		$ (339,492)
Cash and cash equivalents		$ 31,063	$ 16,203	$ 31,063	$ 16,203	$ 17,031	$ 6,359
Common stock, par value | $ / shares	$ 0.01	$ 0.01		$ 0.01		$ 0.01
Reverse split of common stock				one-for-fifteen
Reverse stock split ratio	0.067