Employee and Retiree Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2023

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 and nine-month periods ended September 30, 2023 and 2022.

	Three Months Ended September 30,
	Pension Benefits				Other Postretirement Benefits
(Thousands of dollars)	2023		2022		2023		2022
Service cost	$	1,650	$	2,129	$	132	$	292
Interest cost	8,534		5,163		874		574
Expected return on plan assets	(8,223)		(7,999)		–		–
Estimated defined contribution provision	53		–		–		–
Amortization of prior service cost (credit)	155		582		(133)		(133)
Recognized actuarial loss (gain)	2,407		3,822		(767)		(77)
Total net periodic benefit expense	$	4,576	$	3,697	$	106	$	656
	Nine Months Ended September 30,
	Pension Benefits				Other Postretirement Benefits
(Thousands of dollars)	2023		2022		2023		2022
Service cost	$	4,950	$	6,387	$	396	$	876
Interest cost	25,605		15,545		2,622		1,722
Expected return on plan assets	(24,671)		(24,091)		–		–
Estimated defined contribution provision	161		–		–		–
Amortization of prior service cost (credit)	465		1,761		(399)		(399)
Recognized actuarial loss (gain)	7,222		11,466		(2,315)		(232)
Total net periodic benefit expense	$	13,732	$	11,068	$	304	$	1,967