Nature of Business, Financial Condition and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Apr. 15, 2015 $ / shares	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)
Accounting Policies [Abstract]
Net loss		$ (21,487)	$ (14,370)	$ (25,090)	$ (21,713)
Deficit accumulated		(364,583)		(364,583)		$ (339,492)
Cash and cash equivalents		$ 22,617	$ 22,528	$ 22,617	$ 22,528	$ 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