Warrants - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2009	Dec. 31, 2013	Jun. 30, 2014 Liability	Dec. 31, 2013 Liability	Dec. 31, 2009 J. P. Morgan Securities LLC	Dec. 31, 2013 Registered direct offering
Class of Warrant or Right [Line Items]
Warrants to purchase an aggregate of shares of common stock					8,206,520		184,367
Warrants issued									464,520
Exercise price of Warrants decreased								$ 3.93	$ 4.02
Warrant exercisable Period									6 months
Warrant term					5 years
Estimated fair value of warrant					$ 22,900,000
Expected volatility					105.00%
Risk-free interest rate					2.14%
Expected life in years					5 years
Expected dividend yield					0.00%
Sale of stock price per share										$ 3.50
Warrants outstanding	10,496,467		10,496,467			10,539,767	8,235,076	8,235,076
Change in fair value of warrants	$ 5,600,000	$ (403,000)	$ 5,682,000	$ 10,385,000