Employee and Retiree Benefit Plans (Tables)

3 Months Ended

Mar. 31, 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 periods ended March 31, 2022 and 2021.

	Three Months Ended March 31,
	Pension Benefits			Other Postretirement Benefits
(Thousands of dollars)	2022		2021	2022	2021
Service cost	$	2,129	1,768	292	326
Interest cost	5,243		4,286	574	521
Expected return on plan assets	(8,138)		(6,133)	—	—
Amortization of prior service cost (credit)	600		156	(133)	—
Recognized actuarial loss	3,822		5,279	(77)	(7)
Net periodic benefit expense	$	3,656	5,356	656	840