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Warrant Liability (Details 1) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Assumptions used for the Black-Scholes option pricing model      
Expected life (years) 6 years 4 months 24 days 7 years 4 months 24 days 7 years 2 months 12 days
Fair value of warrant liability $ 9,265,365 $ 6,042,315  
Change in fair value of warrant liability (5,944,571) 6,612,092 3,005,040
Warrant agreement 2009 [Member]
      
Assumptions used for the Black-Scholes option pricing model      
Expected life (years) 2 years 3 months 18 days 3 years 3 months 18 days  
Risk-free interest rate 0.30% 0.50%  
Expected volatility 94.50% 90.80%  
Expected dividend yield 0.00% 0.00%  
Fair value of warrant liability 63,340 28,971  
Change in fair value of warrant liability $ 34,369