v3.26.1
Employee and Retiree Benefit Plans (Tables)
 6 Months Ended
Jun. 30, 2026
Retirement Benefits [Abstract]  
Schedule of Components of Net Periodic Benefit Expense
The table that follows provides the components of net periodic benefit expense for the three and six months ended June 30, 2026 and 2025.
Three Months Ended June 30,
Pension BenefitsOther Postretirement Benefits
(Thousands of dollars)2026202520262025
Service cost$1,865 $1,683 $102 $84 
Interest cost7,752 8,482 750 708 
Expected return on plan assets(8,792)(8,953)— — 
Estimated defined contribution provision70 62 — — 
Amortization of prior service cost (credit)432 492 (133)(133)
Recognized actuarial (gain) loss 1,644 1,914 (387)(1,057)
Total net periodic benefit cost (credit)$2,971 $3,680 $332 $(398)
Six Months Ended June 30,
Pension BenefitsOther Postretirement Benefits
(Thousands of dollars)2026202520262025
Service cost$3,730 $3,366 $204 $168 
Interest cost15,504 16,880 1,500 1,416 
Expected return on plan assets(17,584)(17,824)— — 
Estimated defined contribution provision140 122 — — 
Amortization of prior service cost (credit) 864 983 (266)(266)
Recognized actuarial (gain) loss3,288 3,805 (774)(2,113)
         Total net periodic benefit cost (credit)$5,942 $7,332 $664 $(795)