Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Assets:
Cash equivalents	$ 5,028,053	$ 4,107,478
Total	5,028,053	4,107,478
Liabilities:
Common stock warrants	890,105	5,307,332
Total	890,105	5,307,332
Fair Value, Inputs, Level 1
Assets:
Total	5,028,053	4,107,478
Liabilities:
Total	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	5,028,053	4,107,478
Liabilities:
Common stock warrants	0	0
Fair Value, Inputs, Level 2
Assets:
Total	0	0
Liabilities:
Total	0	0
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0	0
Liabilities:
Common stock warrants	0	0
Fair Value, Inputs, Level 3
Assets:
Total	0	0
Liabilities:
Total	890,105	5,307,332
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0	0
Liabilities:
Common stock warrants	$ 890,105	$ 5,307,332