Fair Value of Financial Instruments (Details 2) (Common stock warrant, USD $)	3 Months Ended
	Mar. 31, 2013
Assumptions used to calculate fair value of common stock warrant liability using Monte-Carlo simulation on a Black-Scholes lattice model
Volatility (as a percent)	70.00%
Stock Price (in dollars per share)	$ 5.62
Dividend Yield (as a percent)	0.00%
Minimum
Assumptions used to calculate fair value of common stock warrant liability using Monte-Carlo simulation on a Black-Scholes lattice model
Exercise Price (in dollars per share)	$ 4
Term	7 years 7 months 6 days
Risk-Free Rate (as a percent)	1.40%
Maximum
Assumptions used to calculate fair value of common stock warrant liability using Monte-Carlo simulation on a Black-Scholes lattice model
Exercise Price (in dollars per share)	$ 5
Term	8 years 8 months 12 days
Risk-Free Rate (as a percent)	1.60%