v3.26.1
Employee and Retiree Benefit Plans (Tables)
3 Months Ended
Mar. 31, 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-month periods ended March 31, 2026 and 2025.
Three Months Ended March 31,
Pension BenefitsOther Postretirement Benefits
(Thousands of dollars)2026202520262025
Service cost$1,865 $1,683 $102 $84 
Interest cost7,752 8,398 750 708 
Expected return on plan assets(8,792)(8,871) — 
Estimated defined contribution provision70 60  — 
Amortization of prior service cost (credit)432 491 (133)(133)
Recognized actuarial (gain) loss 1,644 1,891 (387)(1,056)
Total net periodic benefit cost (credit)$2,971 $3,652 $332 $(397)