Warrants - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended		12 Months Ended	115 Months Ended		3 Months Ended		12 Months Ended	1 Months Ended		12 Months Ended		12 Months Ended
	Feb. 23, 2007	May 03, 2006	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2009 Y	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Liability Warrants	Mar. 31, 2012 Liability Warrants	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, 2009 Registered direct offering
Class of Warrant or Right [Line Items]
Warrant issued	1,359,317	706,708										419,786
Warrant exercised											419,207	11,083
Warrant outstanding			11,148,139			11,148,139	11,197,454					408,703
Value of warrant issued												$ 1,600,000
Sale of stock price per share												$ 4.75	$ 1.825	$ 4.63
Revised price for warrants												$ 4.69	$ 4.25		$ 3.93
Common stock warrants exercise price													$ 2.04
Issuable price for common stock															$ 3.10
Warrant expired											579
Warrants to purchase an aggregate of shares of common stock					8,206,520
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					2.14%
Expected life					5
Expected dividend yield					0.00%
Other income (expense)			$ (4,000)	$ (26,000)		$ 4,697,000		$ 10,800,000	$ (5,800,000)
Warrants expiration date	Feb. 23, 2012	May 03, 2013
Warrant exercise price	5.75	5.09