Net loss per share (Details) - shares |
6 Months Ended | |
|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
|
| Net loss per share | ||
| Potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding | 2,440,629 | 11,235,145 |
| Convertible preferred shares | ||
| Net loss per share | ||
| Potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding | 9,433,910 | |
| Share options and unvested restricted share awards | ||
| Net loss per share | ||
| Potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding | 2,440,629 | 1,801,235 |