Retirement Plans and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2023

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,
	2023		2022		2023		2022		2023		2022		2023		2022
Service cost — benefits earned during the period	$	9,865	$	13,868	$	29,595	$	41,605	$	2,142	$	4,117	$	6,426	$	12,352
Non-service costs (credits):
Interest cost on benefit obligation	38,390		26,873		115,170		80,619		5,627		4,372		16,882		13,118
Expected return on plan assets	(45,735)		(46,443)		(137,204)		(139,331)		(10,872)		(11,510)		(32,616)		(34,531)
Amortization of:
Prior service credit	—		—		—		—		(9,447)		(9,447)		(28,341)		(28,341)
Net actuarial loss/(gain)	9,605		4,379		28,815		13,136		(2,404)		(3,209)		(7,211)		(9,627)
Net periodic cost/(benefit)	$	12,125	$	(1,323)	$	36,376	$	(3,971)	$	(14,954)	$	(15,677)	$	(44,860)	$	(47,029)
Portion of cost/(benefit) charged to expense	$	6,828	$	(4,246)	$	20,568	$	(12,258)	$	(10,851)	$	(11,318)	$	(32,536)	$	(33,736)