Fair Value Measurements - Reconciliation of Company's Financial Liabilities Measured at Fair Value on Recurring Basis 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 |
|
| Warrant Liabilities [Member] | ||||
| Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | ||||
| Balance at beginning of period | $ 525,059 | $ 4,263,124 | $ 313,004 | $ 3,088,017 |
| Issuances of convertible notes | 611,376 | 865,635 | ||
| Increase (Decrease) in fair value | (3,659) | 774,748 | 208,396 | 1,695,596 |
| Balance at end of period | $ 521,400 | 5,649,248 | $ 521,400 | 5,649,248 |
| Embedded Derivatives Liabilities [Member] | ||||
| Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | ||||
| Balance at beginning of period | 1,944,103 | 2,680,780 | ||
| Issuances of convertible notes | 278,805 | 537,607 | ||
| Increase (Decrease) in fair value | (76,166) | (1,071,645) | ||
| Balance at end of period | $ 2,146,742 | $ 2,146,742 | ||