v3.26.1
Retirement Plans and Other Postretirement Benefits - Schedule of Net Periodic Benefit Costs and Portion including Portion Charged to Expense (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Amortization of:        
Portion of costs (credits) charged to expense $ (5,018) $ (3,692) $ (9,000) $ (6,650)
Pension Plans        
Defined Benefit Plan Disclosure [Line Items]        
Service cost-benefits earned during the period 11,684 11,127 23,783 22,076
Non-service costs (credits):        
Interest cost on benefit obligation 37,292 38,584 74,904 77,560
Expected return on plan assets (44,365) (44,849) (88,461) (89,396)
Amortization of:        
Prior service cost (credit) 151 0 302 0
Net actuarial loss (gain) 10,443 11,248 21,596 23,366
Net periodic benefit costs (credits) 15,205 16,110 32,124 33,606
Portion of costs (credits) charged to expense 8,262 9,365 17,780 19,826
Other Benefits Plans        
Defined Benefit Plan Disclosure [Line Items]        
Service cost-benefits earned during the period 2,140 2,059 4,377 4,041
Non-service costs (credits):        
Interest cost on benefit obligation 4,931 5,070 9,910 10,172
Expected return on plan assets (12,719) (12,142) (25,438) (24,284)
Amortization of:        
Prior service cost (credit) 0 0 0 (1,265)
Net actuarial loss (gain) (2,746) (2,965) (5,446) (5,864)
Net periodic benefit costs (credits) (8,394) (7,978) (16,597) (17,200)
Portion of costs (credits) charged to expense $ (6,644) $ (6,399) $ (13,153) $ (13,272)