Fair Value Hierarchy for Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) | Dec. 31, 2015 | Dec. 31, 2014 |
Liabilities | | |
Derivative Liabilities Noncurrent | $ 4,750,687 | $ 6,671,524 |
Fair Value, Measurements, Recurring | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 4,750,687 | 6,671,524 |
Fair Value, Measurements, Recurring | Warrant liability - 2010 Class B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 28,066 |
Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 1,753,969 | |
Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A&B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 3,520,319 |
Fair Value, Measurements, Recurring | Warrant liability - 2012 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 7,661 | 67,246 |
Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 2,985,512 | |
Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D&E | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 3,036,986 |
Fair Value, Measurements, Recurring | Warrant liability - 2013 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 3,545 | 18,907 |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | 0 |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Warrant liability - 2010 Class B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 0 |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A&B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 0 |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Warrant liability - 2012 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | 0 |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D&E | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 0 |
Quoted Market Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Warrant liability - 2013 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Warrant liability - 2010 Class B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 0 |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A&B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 0 |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Warrant liability - 2012 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D&E | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 0 |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Warrant liability - 2013 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 4,750,687 | 6,671,524 |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Warrant liability - 2010 Class B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 28,066 |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 1,753,969 | |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Warrant liability - 2012 Series A&B | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 3,520,319 |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Warrant liability - 2012 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 7,661 | 67,246 |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D | | |
Liabilities | | |
Derivative Liabilities Noncurrent | 2,985,512 | |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Warrant liability - 2013 Series D&E | | |
Liabilities | | |
Derivative Liabilities Noncurrent | | 3,036,986 |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Warrant liability - 2013 placement agent | | |
Liabilities | | |
Derivative Liabilities Noncurrent | $ 3,545 | $ 18,907 |