Employee and Retiree Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2025

Retirement Benefits [Abstract]

Schedule of 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, 2025 and 2024.

	Three Months Ended March 31,
	Pension Benefits				Other Postretirement Benefits
(Thousands of dollars)	2025		2024		2025		2024
Service cost	$	1,683	$	1,706	$	84	$	135
Interest cost	8,398		8,391		708		782
Expected return on plan assets	(8,871)		(8,357)		—		—
Estimated defined contribution provision	60		55		—		—
Amortization of prior service cost (credit)	491		579		(133)		(133)
Recognized actuarial loss (gain)	1,891		2,360		(1,056)		(812)
Total net periodic benefit expense	$	3,652	$	4,734	$	(397)	$	(28)