Employee benefit plans

9 Months Ended

Sep. 30, 2023

Retirement Benefits [Abstract]

Employee benefit plans

Employee benefit plans

Pension and other postretirement plans

The Company has noncontributory qualified defined benefit pension plans and other postretirement benefit plans for certain eligible employees.

In connection with the previously discussed separation of Knife River on May 31, 2023, Knife River's pension plan, including the associated assets and liabilities, was transferred to Knife River and therefore is no longer reflected as part of the Company. Also in connection with the separation, a remeasurement of the Company's postretirement plan and the Company's unfunded, non-qualified defined benefit plan were performed and the applicable liabilities from the plans relating to transferring employees were transferred to Knife River.

Components of net periodic benefit credit for the Company's pension benefit plans were as follows:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2023		2022		2023		2022
	(In thousands)
Components of net periodic benefit credit:
Interest cost	$	3,380	$	2,349	$	10,140	$	7,047
Expected return on assets	(4,299)		(4,370)		(12,897)		(13,112)
Amortization of net actuarial loss	773		1,456		2,319		4,370
Net periodic benefit credit	$	(146)	$	(565)	$	(438)	$	(1,695)

Components of net periodic benefit credit for the Company's other postretirement benefit plans were as follows:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2023		2022		2023		2022
	(In thousands)
Components of net periodic benefit credit:
Service cost	$	131	$	223	$	405	$	669
Interest cost	489		346		1,467		1,038
Expected return on assets	(1,334)		(1,319)		(4,026)		(3,957)
Amortization of prior service credit	(330)		(330)		(989)		(989)
Amortization of net actuarial gain	(96)		(142)		(408)		(425)
Net periodic benefit credit, including amount capitalized	(1,140)		(1,222)		(3,551)		(3,664)
Less amount capitalized	23		47		76		131
Net periodic benefit credit	$	(1,163)	$	(1,269)	$	(3,627)	$	(3,795)

The components of net periodic benefit credit, other than the service cost component, are included in other income on the Consolidated Statements of Income. The service cost component is included in operation and maintenance expense on the Consolidated Statements of Income.

Nonqualified defined benefit plans

In addition to the qualified defined benefit pension plans reflected in the table at the beginning of this note, the Company also has unfunded, nonqualified defined benefit plans for executive officers and certain key management employees. The Company's net periodic benefit cost for these plans was $759,000 and $648,000 for the three months ended September 30, 2023 and 2022, respectively, and $2.3 million and $1.9 million for the nine months ended September 30, 2023 and 2022 respectively. The components of net periodic benefit cost for these plans are included in other income on the Consolidated Statements of Income.