Preferred Stock and Warrants - Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Jun. 02, 2014	Dec. 31, 2015	Dec. 31, 2013	Apr. 30, 2015	Dec. 31, 2014
2013 Warrants
Temporary Equity [Line Items]
Warrants issued			1,079,453
Warrants expiration date		Jun. 02, 2019
Deerfield Warrant
Temporary Equity [Line Items]
Warrants issued	14,423,076
Warrants expiration date	Jun. 02, 2024
Convertible Notes
Temporary Equity [Line Items]
Debt instrument issued			$ 3.8
Series D Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock called by warrants			1,079,453	15,499,324	15,502,529
Warrant, exercise price					$ 0.78
Redeemable convertible preferred stock, exercise of Series D Preferred warrants		3,205
Common stock
Temporary Equity [Line Items]
Preferred stock called by warrants			143,466	2,066,543
Warrant, exercise price			$ 5.85
Common stock | Deerfield Warrant
Temporary Equity [Line Items]
Preferred stock called by warrants	1,923,077
Warrant, exercise price	$ 5.85