Fair Value Measurement - Financial Assets and Liabilities Measured at Fair Value (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Outstanding warrants [Member]
Financial liabilities:
Total financial liabilities	$ 5,868,000
Fair Value, Measurements [Member]
Financial assets:
Total financial assets	26,032,328
Financial liabilities:
Total financial liabilities	21,783,602
Fair Value, Measurements [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	1,121,349
Fair Value, Measurements [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	24,910,979
Fair Value, Measurements [Member] \| Bond obligation [Member]
Financial liabilities:
Total financial liabilities	71,250
Fair Value, Measurements [Member] \| Loan Payable [Member]
Financial liabilities:
Total financial liabilities	15,843,919
Fair Value, Measurements [Member] \| Outstanding warrants [Member]
Financial liabilities:
Total financial liabilities	5,868,433
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member]
Financial assets:
Total financial assets	26,032,328
Financial liabilities:
Total financial liabilities
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	1,121,349
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	24,910,979
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member] \| Bond obligation [Member]
Financial liabilities:
Total financial liabilities
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member] \| Loan Payable [Member]
Financial liabilities:
Total financial liabilities
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member] \| Outstanding warrants [Member]
Financial liabilities:
Total financial liabilities
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements [Member]
Financial assets:
Total financial assets
Financial liabilities:
Total financial liabilities	71,250
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements [Member] \| Bond obligation [Member]
Financial assets:
Total financial assets	71,250	125,000
Financial liabilities:
Total financial liabilities	71,250
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements [Member] \| Loan Payable [Member]
Financial liabilities:
Total financial liabilities
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements [Member] \| Outstanding warrants [Member]
Financial liabilities:
Total financial liabilities
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member]
Financial assets:
Total financial assets
Financial liabilities:
Total financial liabilities	21,712,352
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member] \| Bond obligation [Member]
Financial liabilities:
Total financial liabilities
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member] \| Loan Payable [Member]
Financial liabilities:
Total financial liabilities	15,843,919
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member] \| Outstanding warrants [Member]
Financial liabilities:
Total financial liabilities	$ 5,868,433