|
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% |