Shareholders' equity (deficit) - Share-based compensation - Non-vested share options (Details) - $ / shares |
6 Months Ended | |
|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
|
| Number of options | ||
| Non-vested at beginning of period | 1,706,303 | 451,113 |
| Forfeited/expired | (12,198) | |
| Vested, outstanding | (200,889) | (88,600) |
| Non-vested share options at end of period | 1,669,151 | 1,237,747 |
| Weighted average fair value | ||
| Non-vested at beginning of period | $ 1.3458 | $ 1.0266 |
| Forfeited/expired | 1.0639 | |
| Vested, outstanding | 1.1787 | 1.0958 |
| Non-vested at end of period | $ 2.0041 | $ 1.0798 |
| 2011 Plan | ||
| Number of options | ||
| Granted | 116,739 | 887,432 |
| Weighted average fair value | ||
| Granted | $ 6.6491 | $ 1.1114 |
| 2019 Plan | ||
| Number of options | ||
| Granted | 46,998 | |
| Weighted average fair value | ||
| Granted | $ 10.7731 | |