Employee Benefit Plans: (Tables)

6 Months Ended

Jun. 30, 2023

Schedule of components of net periodic benefit costs, before allocation to the overhead pool, for Registrant's pension plan, postretirement plan, and SERP

The components of net periodic benefit costs for Registrant’s pension plan, postretirement medical benefit plan and SERP for the three and six months ended June 30, 2023 and 2022 were as follows:


	For The Three Months Ended June 30,
	Pension Benefits				Other Postretirement Benefits				SERP
(dollars in thousands)	2023		2022		2023		2022		2023		2022
Components of Net Periodic Benefits Cost:
Service cost	$	846	$	1,342	$	33	$	33	$	312	$	298
Interest cost	2,513		1,856		26		16		411		256
Expected return on plan assets	(2,623)		(3,290)		(119)		(147)		—		—
Amortization of prior service cost	108		109		—		—		—		—
Amortization of actuarial (gain) loss	—		—		(242)		(412)		(8)		145
Net periodic benefits costs under accounting standards	844		17		(302)		(510)		715		699
Regulatory adjustments - deferred	(92)		—		—		—		—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	752	$	17	$	(302)	$	(510)	$	715	$	699


	For The Six Months Ended June 30,
	Pension Benefits				Other Postretirement Benefits				SERP
(dollars in thousands)	2023		2022		2023		2022		2023		2022
Components of Net Periodic Benefits Cost:
Service cost	$	1,692	$	2,822	$	66	$	66	$	624	$	596
Interest cost	5,026		3,700		51		32		822		512
Expected return on plan assets	(5,246)		(6,582)		(239)		(294)		—		—
Amortization of prior service cost	216		218		—		—		—		—
Amortization of actuarial (gain) loss	—		—		(482)		(824)		(16)		290
Net periodic benefits costs under accounting standards	1,688		158		(604)		(1,020)		1,430		1,398
Regulatory adjustments - deferred	(184)		—		—		—		—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	1,504	$	158	$	(604)	$	(1,020)	$	1,430	$	1,398