Fair Value Measurement - Financial Assets and Liabilities Measured at Fair Value (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Outstanding Warrants [Member]
Financial liabilities:
Total financial liabilities	$ 8,525,666
Fair Value, Measurements [Member]
Financial assets:
Total financial assets	17,334,018
Financial liabilities:
Total financial liabilities	19,650,488
Fair Value, Measurements [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	421,373
Fair Value, Measurements [Member] \| U.S. Treasury debt obligations [Member] \| Cash equivalents [Member]
Financial assets:
Total financial assets	16,912,645
Fair Value, Measurements [Member] \| Bonds payable [Member]
Financial liabilities:
Total financial liabilities	17,917
Fair Value, Measurements [Member] \| Loan Payable [Member]
Financial liabilities:
Total financial liabilities	11,106,905
Fair Value, Measurements [Member] \| Outstanding Warrants [Member]
Financial liabilities:
Total financial liabilities	8,525,666
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member]
Financial assets:
Total financial assets	17,334,018
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	421,373
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	16,912,645
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements [Member] \| Bonds payable [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	17,917
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] \| Bonds payable [Member]
Financial assets:
Total financial assets	17,917	125,000
Financial liabilities:
Total financial liabilities	17,917
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	19,632,571
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] \| Bonds payable [Member]
Financial liabilities:
Total financial liabilities
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member] \| Loan Payable [Member]
Financial liabilities:
Total financial liabilities	11,106,905
Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements [Member] \| Outstanding Warrants [Member]
Financial liabilities:
Total financial liabilities	$ 8,525,666