Employee retirement plans - Schedule of Pension Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Retirement Benefits [Abstract] | ||||
| Pension expense | $ 361 | $ 455 | $ 711 | $ 843 |