Fair Value Measurement (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Financial assets:
Total financial assets	$ 10,181,831	$ 14,339,896
Fair Value, Measurements [Member]
Financial assets:
Total financial assets	16,425,756
Financial liabilities:
Total financial liabilities	9,316,382
Fair Value, Measurements [Member] \| Bond obligation [Member]
Financial liabilities:
Total financial liabilities	281,250
Fair Value, Measurements [Member] \| Warrant liabilities [Member]
Financial liabilities:
Total financial liabilities	9,035,132
Fair Value, Measurements [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	321,197
Fair Value, Measurements [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	6,287,050
Fair Value, Measurements [Member] \| Debt securities [Member] \| Marketable securities [Member]
Financial assets:
Total financial assets	9,817,509
Fair Value, Measurements [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Total financial assets	6,608,247
Financial liabilities:
Total financial liabilities
Fair Value, Measurements [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Bond obligation [Member]
Financial liabilities:
Total financial liabilities
Fair Value, Measurements [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Warrant liabilities [Member]
Financial liabilities:
Total financial liabilities
Fair Value, Measurements [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	321,197
Fair Value, Measurements [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	6,287,050
Fair Value, Measurements [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Debt securities [Member] \| Marketable securities [Member]
Financial assets:
Total financial assets
Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Total financial assets	9,817,509
Financial liabilities:
Total financial liabilities	364,322
Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Bond obligation [Member]
Financial liabilities:
Total financial liabilities	281,250
Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Warrant liabilities [Member]
Financial liabilities:
Total financial liabilities	83,072
Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Debt securities [Member] \| Marketable securities [Member]
Financial assets:
Total financial assets	9,817,509
Fair Value, Measurements [Member] \| Unobservable Inputs (Level 3) [Member]
Financial assets:
Total financial assets
Financial liabilities:
Total financial liabilities	8,952,060
Fair Value, Measurements [Member] \| Unobservable Inputs (Level 3) [Member] \| Bond obligation [Member]
Financial liabilities:
Total financial liabilities
Fair Value, Measurements [Member] \| Unobservable Inputs (Level 3) [Member] \| Warrant liabilities [Member]
Financial liabilities:
Total financial liabilities	8,952,060
Fair Value, Measurements [Member] \| Unobservable Inputs (Level 3) [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Fair Value, Measurements [Member] \| Unobservable Inputs (Level 3) [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Fair Value, Measurements [Member] \| Unobservable Inputs (Level 3) [Member] \| Debt securities [Member] \| Marketable securities [Member]
Financial assets:
Total financial assets