v3.26.3
Pensions and other postretirement benefit plans - Schedule of Components of Net Periodic Pension and Postretirement Benefits (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Pension benefits        
Defined Benefit Plan Disclosure        
Service cost - benefits earned during the period $ 224 $ 248 $ 672 $ 744
Interest cost on benefit obligations 17,492 20,919 52,480 62,143
Expected return on plan assets (20,591) (23,550) (61,778) (69,854)
Amortization of prior service cost (benefit) 19 18 55 53
Amortization of actuarial loss (gain) 708 628 2,124 1,825
Total benefit, net (2,148) (1,737) (6,447) (5,089)
Postretirement benefits        
Defined Benefit Plan Disclosure        
Service cost - benefits earned during the period 7 8 20 24
Interest cost on benefit obligations 464 527 1,391 1,579
Expected return on plan assets 0 0 0 0
Amortization of prior service cost (benefit) (143) (143) (427) (427)
Amortization of actuarial loss (gain) (396) (419) (1,188) (1,256)
Total benefit, net $ (68) $ (27) $ (204) $ (80)