Fair Value of Financial Instruments (Details 3) (Binomial tree, Recurring basis, Level 3, USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Derivative liabilities | 2008 Warrants
Assumptions used in the valuation models to determine the fair value of the derivative liabilities
Exercise price (in dollars per share)	$ 9.05	$ 9.05
Volatility (as a percent)	103.67%	78.43%
Stock price (in dollars per share)	$ 0.37	$ 2.15
Risk-free discount rate (as a percent)	0.16%	0.19%
Derivative liabilities | 2010 Warrants
Assumptions used in the valuation models to determine the fair value of the derivative liabilities
Exercise price (in dollars per share)	$ 3.84	$ 3.84
Volatility (as a percent)	103.67%	78.43%
Stock price (in dollars per share)	$ 0.37	$ 2.15
Risk-free discount rate (as a percent)	0.50%	0.83%
Conversion feature embedded in derivative liability | Series B-1 Preferred Stock
Assumptions used in the valuation models to determine the fair value of the derivative liabilities
Exercise price (in dollars per share)	$ 15.95	$ 15.95
Volatility (as a percent)	103.67%	78.43%
Stock price (in dollars per share)	$ 0.37	$ 2.15
Option Adjusted Spread (as a percent)	58.46%	30.60%
Risk-free discount rate (as a percent)	0.34%	0.59%
Preferred adjustment (as a percent)	1.51%	0.82%