Retirement Plans and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2022

Schedule of net periodic benefit costs and the portion of these costs charged to expense (including administrative costs and excluding amounts capitalized as overhead construction, billed to electric plant participants or charged or amortized to the regulatory asset)

The following table provides details of the plans’ net periodic benefit costs and the portion of these costs charged to expense (including administrative costs and excluding amounts capitalized as overhead construction or billed to electric plant participants) (dollars in thousands):


	Pension Benefits								Other Benefits
	Three Months Ended September 30,				Nine Months Ended September 30,				Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021		2022		2021		2022		2021
Service cost — benefits earned during the period	$	13,868	$	15,309	$	41,605	$	45,927	$	4,117	$	4,449	$	12,352	$	13,347
Non-service costs (credits):
Interest cost on benefit obligation	26,873		24,641		80,619		73,924		4,372		4,128		13,118		12,385
Expected return on plan assets	(46,443)		(50,657)		(139,331)		(151,971)		(11,510)		(10,361)		(34,531)		(31,083)
Amortization of:
Prior service credit	—		—		—		—		(9,447)		(9,425)		(28,341)		(28,279)
Net actuarial loss (gain)	4,379		3,987		13,136		11,961		(3,209)		(2,523)		(9,627)		(7,569)
Net periodic benefit	$	(1,323)	$	(6,720)	$	(3,971)	$	(20,159)	$	(15,677)	$	(13,732)	$	(47,029)	$	(41,199)
Portion of benefit charged to expense	$	(4,246)	$	(7,803)	$	(12,258)	$	(24,428)	$	(11,318)	$	(9,765)	$	(33,736)	$	(28,901)