Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2009
Class of Warrant or Right [Line Items]
Warrants to purchase an aggregate of shares of common stock			8,206,520
Warrant term			5 years
Warrants expiration date	2014-12
Gain on expiration of liability-classified warrants		$ 195
Warrants exercised		4,004,907
Conversion of Warrants to Common Stock		3,725,277
Liability
Class of Warrant or Right [Line Items]
Warrants outstanding		1,755,845
Warrants expired		6,479,231
Equity
Class of Warrant or Right [Line Items]
Warrants outstanding		2,249,062
Warrants expired		12,329
Private Placement
Class of Warrant or Right [Line Items]
Warrants to purchase an aggregate of shares of common stock			2,910,954
Warrant exercise price			$ 2.04
Warrant exercisable Period			5 years
Estimated fair value of warrant			$ 4,200
Private Placement | Warrants
Class of Warrant or Right [Line Items]
Expected volatility			105.00%
Risk-free interest rate			2.41%
Expected life in years			5 years
Expected dividend yield			0.00%
J. P. Morgan Securities LLC
Class of Warrant or Right [Line Items]
Warrants issued			464,520
Placement Agents | Private Placement
Class of Warrant or Right [Line Items]
Warrants to purchase an aggregate of shares of common stock			138,617