v3.25.4
Employee benefit plans - Financial Position of Defined Benefit Plans (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Amounts recognized in the consolidated balance sheets consist of:      
Accrued pension benefit cost included in employee benefit plans liability $ (84,466) $ (83,589)  
Pension plans      
Defined Benefit Plan Disclosure [Line Items]      
Accumulated benefit obligation at end of year 100,397 99,013 $ 110,004
Change in projected benefit obligation      
Projected benefit obligation at beginning of year 99,013 110,004 106,748
Service cost 0 0 0
Interest cost 5,235 5,134 5,367
Benefits paid (7,901) (7,961) (7,829)
Actuarial (gain) loss 1,122 (7,453) 3,368
Foreign exchange translation adjustment 2,928 (711) 2,350
Projected benefit obligation at end of year 100,397 99,013 110,004
Change in plan assets      
Fair value of plan assets at beginning of year 126,419 136,653 137,294
Actual return on plan assets 8,950 (1,501) 3,725
Employer contribution 10,174 153 386
Benefits paid (7,901) (7,961) (7,829)
Foreign exchange translation adjustment 3,781 (925) 3,077
Fair value of plan assets at end of year 141,423 126,419 136,653
Amounts recognized in the consolidated balance sheets consist of:      
Prepaid benefit cost included in accrued interest and other assets 41,037 27,417 26,661
Accrued pension benefit cost included in employee benefit plans liability (11) (11) (12)
Surplus (deficit) of plan assets over projected benefit obligation at measurement date 41,026 27,406 26,649
Post- retirement medical benefit plan      
Defined Benefit Plan Disclosure [Line Items]      
Accumulated benefit obligation at end of year 84,455 83,578 88,682
Change in projected benefit obligation      
Projected benefit obligation at beginning of year 83,578 88,682 91,983
Service cost 43 54 76
Interest cost 4,369 4,385 4,786
Benefits paid (2,664) (3,324) (3,244)
Actuarial (gain) loss (871) (6,219) (4,919)
Foreign exchange translation adjustment 0 0 0
Projected benefit obligation at end of year 84,455 83,578 88,682
Change in plan assets      
Fair value of plan assets at beginning of year 0 0 0
Actual return on plan assets 0 0 0
Employer contribution 2,664 3,324 3,244
Benefits paid (2,664) (3,324) (3,244)
Foreign exchange translation adjustment 0 0 0
Fair value of plan assets at end of year 0 0 0
Amounts recognized in the consolidated balance sheets consist of:      
Prepaid benefit cost included in accrued interest and other assets 0 0 0
Accrued pension benefit cost included in employee benefit plans liability (84,455) (83,578) (88,682)
Surplus (deficit) of plan assets over projected benefit obligation at measurement date $ (84,455) $ (83,578) $ (88,682)