Employee Benefit Plans: (Tables)

9 Months Ended

Sep. 30, 2021

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 nine months ended September 30, 2021 and 2020 were as follows:


	For The Three Months Ended September 30,
	Pension Benefits				Other Postretirement Benefits				SERP
(dollars in thousands)	2021		2020		2021		2020		2021		2020
Components of Net Periodic Benefits Cost:
Service cost	$	1,487	$	1,390	$	31	$	35	$	348	$	244
Interest cost	1,700		1,970		22		44		229		247
Expected return on plan assets	(3,137)		(2,950)		(134)		(130)		—		—
Amortization of prior service cost	109		109		—		—		—		—
Amortization of actuarial (gain) loss	876		484		(488)		(334)		419		211
Net periodic benefits costs under accounting standards	1,035		1,003		(569)		(385)		996		702
Regulatory adjustment - deferred	(254)		(121)		—		—		—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	781	$	882	$	(569)	$	(385)	$	996	$	702


	For The Nine Months Ended September 30,
	Pension Benefits				Other Postretirement Benefits				SERP
(dollars in thousands)	2021		2020		2021		2020		2021		2020
Components of Net Periodic Benefits Cost:
Service cost	$	4,737	$	4,170	$	111	$	129	$	1,044	$	732
Interest cost	5,124		5,910		84		156		687		741
Expected return on plan assets	(9,405)		(8,850)		(402)		(384)		—		—
Amortization of prior service cost	327		327		—		—		—		—
Amortization of actuarial (gain) loss	2,862		1,452		(1,062)		(732)		1,257		633
Net periodic benefits costs under accounting standards	3,645		3,009		(1,269)		(831)		2,988		2,106
Regulatory adjustment - deferred	(956)		(362)		—		—		—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	2,689	$	2,647	$	(1,269)	$	(831)	$	2,988	$	2,106