Income taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
|
| Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] | |||
| Balance at the beginning | $ 2,110 | $ 1,313 | $ 644 |
| Increases related to prior year tax positions | 223 | 51 | 66 |
| Increases related to current year tax positions | 1,061 | 746 | 603 |
| Balance at the ending | $ 3,394 | $ 2,110 | $ 1,313 |