v3.26.1
Employee benefit plans - Schedule of Components of Net Periodic Benefit Cost (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, net periodic benefit cost [Line Items]        
Interest cost $ 3,128 $ 3,303 $ 6,256 $ 6,606
Expected return on assets (3,392) (3,645) (6,783) (7,290)
Amortization of net actuarial gain 1,432 1,194 2,864 2,387
Net periodic benefit credit 1,168 852 2,337 1,703
Other postretirement benefits        
Defined benefit plan disclosure, net periodic benefit cost [Line Items]        
Service cost 94 99 188 198
Interest cost 441 462 882 924
Expected return on assets (1,270) (1,292) (2,540) (2,584)
Amortization of prior service credit (45) (289) (90) (579)
Amortization of net actuarial gain (23) (80) (46) (160)
Net periodic benefit credit, including amount capitalized (803) (1,100) (1,606) (2,201)
Less amount capitalized 17 18 35 36
Net periodic benefit credit $ (820) $ (1,118) $ (1,641) $ (2,237)