Fair Value Measurement - Financial Assets and Liabilities Measured at Fair Value (Detail) - Fair Value, Measurements [Member]	Jun. 30, 2015 USD ($)
Financial assets:
Total financial assets	$ 27,626,406
Financial liabilities:
Total financial liabilities	13,426,532
Money market funds [Member] | Cash equivalents [Member]
Financial assets:
Total financial assets	971,527
U.S. Treasury debt obligations [Member] | Cash equivalents [Member]
Financial assets:
Total financial assets	26,654,879
Loan Payable [Member]
Financial liabilities:
Total financial liabilities	12,383,018
Outstanding Warrants [Member]
Financial liabilities:
Total financial liabilities	1,043,514
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Total financial assets	27,626,406
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money market funds [Member] | Cash equivalents [Member]
Financial assets:
Total financial assets	971,527
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	26,654,879
Unobservable Inputs (Level 3) [Member]
Financial liabilities:
Total financial liabilities	13,426,532
Unobservable Inputs (Level 3) [Member] | Loan Payable [Member]
Financial liabilities:
Total financial liabilities	12,383,018
Unobservable Inputs (Level 3) [Member] | Outstanding Warrants [Member]
Financial liabilities:
Total financial liabilities	$ 1,043,514