Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2009	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	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
Other income (expense), net		$ 12	$ (5)	$ (579)
Gain on expiration of liability-classified warrants			$ 195
Warrants exercised			4,004,907	135,346
Conversion of Warrants to Common Stock			3,725,277	112,808
Liability
Class of Warrant or Right [Line Items]
Classified warrants				$ 11,800
Warrants outstanding			1,755,845	0
Warrants expired			6,479,231
Equity
Class of Warrant or Right [Line Items]
Warrants outstanding			2,249,062	135,346
Warrants expired			12,329
Liability Warrants
Class of Warrant or Right [Line Items]
Other income (expense), net				$ (1,200)
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
Warrants exercised	136,986
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