EMPLOYEE BENEFIT PLANS (Notes)

3 Months Ended

Mar. 31, 2024

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

Employee Benefit Plans (Notes)

EMPLOYEE BENEFIT PLANS

The following tables set forth the components of net periodic benefit cost for our pension and other postemployment benefit plans for the periods indicated:

		Pension Benefits
		Three Months Ended March 31,
		2024		2023
	(Thousands of dollars)
Components of net periodic benefit cost (credit)
Service cost		$	1,551	$	1,811
Interest cost (a)		10,281		10,607
Expected return on assets (a)		(14,757)		(14,879)
Amortization of unrecognized prior service cost (a)		93		93
Amortization of net loss (a)		1,446		502
Net periodic benefit cost (credit)		$	(1,386)	$	(1,866)
(a) These amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other income (expense), net in the consolidated statement of income. See Note 11 for additional detail for our other income (expense), net.

	Other Postemployment Benefits
	Three Months Ended March 31,
	2024		2023
	(Thousands of dollars)
Components of net periodic benefit cost (credit)
Service cost	$	152	$	183
Interest cost (a)	2,045		2,288
Expected return on assets (a)	(2,284)		(2,432)
Amortization of unrecognized prior service cost (credit) (a)	—		38
Amortization of net (gain) loss (a)	(4)		(12)
Net periodic benefit cost (credit)	$	(91)	$	65
(a) These amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other income (expense), net in the consolidated statement of income. See Note 11 for additional detail for our other income (expense), net.

We recover qualified pension benefit plan and other postemployment benefit plan costs through rates charged to our customers. Certain regulatory authorities require that the recovery of these costs be based on specific guidelines. The difference between these regulatory-based amounts and the periodic benefit cost calculated pursuant to GAAP is deferred as a regulatory asset or liability and amortized to expense over periods in which this difference will be recovered in rates, as authorized by the applicable regulatory authorities. For the three months ended March 31, 2024 and 2023, regulatory deferrals related to net periodic benefit cost were $1.0 million and $1.4 million, respectively.

We capitalize all eligible service cost and non-service cost components under the accounting requirements of ASC Topic 980 (Regulated Operations) for rate-regulated entities. Capitalized non-service costs reflected as a regulatory asset in our consolidated balance sheets were $3.3 million at March 31, 2024, and were $2.2 million at December 31, 2023. See Note 3 of the Notes to Consolidated Financial Statements in this Quarterly Report for additional information.