Employee retirement plans - Schedule of Pension Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Retirement Benefits [Abstract] | ||||
| Pension expense | $ 401 | $ 463 | $ 1,112 | $ 1,306 |