Employee and Retiree Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2024

Retirement Benefits [Abstract]

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, 2024 and 2023.

	Three Months Ended March 31,
	Pension Benefits				Other Postretirement Benefits
(Thousands of dollars)	2024		2023		2024		2023
Service cost	$	1,706	$	1,650	$	135	$	132
Interest cost	8,391		8,507		782		874
Expected return on plan assets	(8,357)		(8,194)		–		–
Estimated defined contribution provision	55		–		–		–
Amortization of prior service cost (credit)	579		155		(133)		(133)
Recognized actuarial loss (gain)	2,360		2,401		(812)		(781)
Total net periodic benefit expense	$	4,734	$	4,519	$	(28)	$	92