Warrant Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Risk-free interest rate (in hundredths)	0.46%
Expected lives	1 year 7 months 2 days
Expected volatility (in hundredths)	89.70%
(Gain) Loss on warrant liabilities	$ 19,051,239	$ (20,210,094)	$ 2,766,704
July 2009 Equity Public Offering [Member]
Derivative [Line Items]
Warrants expired	544,716
Warrant [Member]
Derivative [Line Items]
Expected dividend yield (in hundredths)	0.00%	0.00%	0.00%
Number of warrants classified as liabilities	6,371,854	6,984,716	6,984,716
(Gain) Loss on warrant liabilities	$ 19,051,239	$ (20,210,094)	$ 2,766,704
Warrant [Member] | Minimum [Member]
Derivative [Line Items]
Risk-free interest rate (in hundredths)		0.13%	0.25%
Expected lives		0 years 11 months 12 days	1 year 11 months 12 days
Expected volatility (in hundredths)		83.40%	72.60%
Warrant [Member] | Maximum [Member]
Derivative [Line Items]
Risk-free interest rate (in hundredths)		0.58%	0.45%
Expected lives		2 years 7 months 2 days	3 years 7 months 2 days
Expected volatility (in hundredths)		95.30%	76.00%