Fair Value Measurement - Roll Forward for Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Less change in fair value of warrants	$ 988,367	$ (3,654,470)	$ 641,037	$ (3,981,094)
Outstanding Warrants [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at March 31, 2015	2,031,881
Less change in fair value of warrants	(988,367)
Balance at June 30, 2015	1,043,514		1,043,514
Balance at June 30, 2015	2,031,881		1,043,514
Loan Payable [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at March 31, 2015	13,372,796
Add amortization of discount	26,612
Less repayments of principal			(1,016,390)
Balance at June 30, 2015	12,383,018		12,383,018
Current portion			3,466,377
Non-current portion			8,916,641
Balance at June 30, 2015	$ 13,372,796		$ 12,383,018