Stockholders' deficit - Common stock reserved for future issuance (Details) - shares |
Sep. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Equity [Abstract] | ||
| Conversion of Series E (in shares) | 1,760,903 | 1,760,903 |
| Exercise of options to purchase common stock (in shares) | 7,241,942 | 7,791,833 |
| Warrants to purchase common stock (in shares) | 19,898,859 | 16,981,854 |
| Notes payable (in shares) | 7,346,568 | 4,437,500 |
| Total (in shares) | 36,248,272 | 30,972,090 |
| X | ||||||||||
- Definition Number of shares of convertible preferred stock issuable upon conversion. No definition available.
|
| X | ||||||||||
- Definition Number of share options (or share units) exercised during the current period. No definition available.
|
| X | ||||||||||
- Definition Number of shares of notes payable issuable upon conversion. No definition available.
|
| X | ||||||||||
- Definition Warrants reserved to purchases shares of common stock. No definition available.
|
| X | ||||||||||
- Definition Aggregate number of common shares reserved for future issuance. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- References No definition available.
|