Commitments and contingencies - Future annual minimum lease payment commitments (Details) $ in Thousands |
Dec. 31, 2019
USD ($)
|
|---|---|
| Commitments and contingencies | |
| 2020 | $ 2,062 |
| 2021 | 2,901 |
| 2022 | 2,493 |
| 2023 | 2,568 |
| 2024 | 2,645 |
| 2025 | 2,725 |
| Thereafter | 12,770 |
| Total | $ 28,164 |