Fair Value (Summary of basis used to measure certain financial assets at fair value on recurring basis) (Details) (Fair Value Measurements, Recurring Basis [Member], Common stock warrants [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock warrant liability	$ 12,895,564	$ 475,825
Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock warrant liability
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock warrant liability
Significant Other Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock warrant liability	$ 12,895,564	$ 475,825