Employee and Retiree Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2022

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, 2022 and 2021.

	Three Months Ended September 30,
	Pension Benefits			Other Postretirement Benefits
(Thousands of dollars)	2022		2021	2022		2021
Service cost	$	2,129	1,770	$	292	328
Interest cost	5,163		4,258	574		521
Expected return on plan assets	(7,999)		(6,038)	—		—
Amortization of prior service cost (credit)	582		155	(133)		—
Recognized actuarial loss (gain)	3,822		5,269	(77)		(8)
Net periodic benefit expense	$	3,697	5,414	$	656	841
	Nine Months Ended September 30,
	Pension Benefits			Other Postretirement Benefits
(Thousands of dollars)	2022		2021	2022		2021
Service cost	$	6,387	5,306	$	876	981
Interest cost	15,545		12,844	1,722		1,563
Expected return on plan assets	(24,091)		(18,326)	—		—
Amortization of prior service cost (credit)	1,761		467	(399)		—
Recognized actuarial loss (gain)	11,466		15,829	(232)		(23)
Net periodic benefit expense	$	11,068	16,120	$	1,967	2,521