Employee and Retiree Benefit Plans (Tables)

6 Months Ended

Jun. 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 six-month periods ended June 30, 2023 and 2022.

	Three Months Ended June 30,
	Pension Benefits				Other Postretirement Benefits
(Thousands of dollars)	2023		2022		2023		2022
Service cost	$	1,650	$	2,129	$	132	$	292
Interest cost	8,564		5,139		874		574
Expected return on plan assets	(8,254)		(7,954)		–		–
Estimated defined contribution provision	54		–		–		–
Amortization of prior service cost (credit)	155		579		(133)		(133)
Recognized actuarial loss (gain)	2,414		3,822		(767)		(78)
Total net periodic benefit expense	$	4,583	3,715		106		655
	Six Months Ended June 30,
	Pension Benefits				Other Postretirement Benefits
(Thousands of dollars)	2023		2022		2023		2022
Service cost	$	3,300	$	4,258	$	264	$	584
Interest cost	17,071		10,382		1,748		1,148
Expected return on plan assets	(16,448)		(16,092)		–		–
Estimated defined contribution provision	108		—		–		–
Amortization of prior service cost (credit)	310		1,179		(266)		(266)
Recognized actuarial loss (gain)	4,815		7,644		(1,548)		(155)
Total net periodic benefit expense	$	9,156	$	7,371	$	198	$	1,311