v3.26.1
Pensions and other postretirement benefit plans - Schedule of Components of Net Periodic Pension and Postretirement Benefits (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension benefits        
Defined Benefit Plan Disclosure        
Service cost - benefits earned during the period $ 224 $ 248 $ 448 $ 496
Interest cost on benefit obligations 17,475 20,837 34,988 41,224
Expected return on plan assets (20,569) (23,444) (41,187) (46,304)
Amortization of prior service cost (benefit) 18 18 36 35
Amortization of actuarial loss (gain) 706 620 1,416 1,197
Total benefit, net (2,146) (1,721) (4,299) (3,352)
Postretirement benefits        
Defined Benefit Plan Disclosure        
Service cost - benefits earned during the period 6 8 13 16
Interest cost on benefit obligations 463 526 927 1,052
Expected return on plan assets 0 0 0 0
Amortization of prior service cost (benefit) (142) (142) (284) (284)
Amortization of actuarial loss (gain) (396) (418) (792) (837)
Total benefit, net $ (69) $ (26) $ (136) $ (53)