Cash and cash equivalents (Details) - USD ($) $ in Thousands |
Jun. 30, 2021 |
Dec. 31, 2020 |
Jun. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|---|---|
| Cash and Cash Equivalents [Abstract] | ||||
| Cash on hand and at banks | $ 73,115 | $ 94,787 | ||
| Short-term deposits and highly liquid funds | 44 | 94 | ||
| Restricted cash | 10 | 16,303 | ||
| Cash and cash equivalents and restricted cash | $ 73,169 | $ 111,184 | $ 55,072 | $ 78,727 |