STOCKHOLDERS' DEFICIT - Reserve Shares of Common Stock (Details) - shares |
Sep. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Class of Stock [Line Items] | ||
| Capital shares reserved for future issuance (in shares) | 28,731,934 | 12,981,599 |
| Stock Options Outstanding | ||
| Class of Stock [Line Items] | ||
| Capital shares reserved for future issuance (in shares) | 8,536,713 | 7,117,002 |
| Warrants to Purchase Common Stock | ||
| Class of Stock [Line Items] | ||
| Capital shares reserved for future issuance (in shares) | 17,035,214 | 1,914,316 |
| Conversion Debt | ||
| Class of Stock [Line Items] | ||
| Capital shares reserved for future issuance (in shares) | 1,635,299 | 1,720,224 |
| Omnibus Incentive Plan 2012 | ||
| Class of Stock [Line Items] | ||
| Capital shares reserved for future issuance (in shares) | 1,524,708 | 2,230,057 |