Warrants - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended	127 Months Ended		3 Months Ended		12 Months Ended	1 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2009	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Liability	Dec. 31, 2013 Liability	Dec. 31, 2009 J. P. Morgan Securities LLC	May 31, 2012 Private Placement	May 31, 2005 Private Placement	Dec. 31, 2009 Private Placement	Dec. 31, 2006 Private Placement	Dec. 31, 2013 Registered direct offering	Dec. 31, 2009 Registered direct offering
Class of Warrant or Right [Line Items]
Warrant issued										419,786
Warrant exercised	0								419,207	11,083
Warrant outstanding	10,539,767			10,539,767	10,539,767	8,235,076	8,235,076			408,703
Value of warrant issued										$ 1,600,000
Sale of stock price per share										$ 4.75	$ 1.825	$ 4.63	$ 3.5	$ 3.10
Revised price for warrants										$ 4.69	$ 4.25			$ 3.93
Common stock warrants, exercise price											2.04
Warrant expired									579
Warrants to purchase an aggregate of shares of common stock			8,206,520			184,367
Warrants issued								464,520
Warrant exercise price								$ 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%
Change in fair value of warrants	$ 82,000	$ 10,788,000		$ 12,038,000