Employee Benefit Plans: (Tables)

9 Months Ended

Sep. 30, 2020

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, 2020 and 2019 were as follows:


	For The Three Months Ended September 30,
	Pension Benefits				Other Postretirement Benefits				SERP
(dollars in thousands)	2020		2019		2020		2019		2020		2019
Components of Net Periodic Benefits Cost:
Service cost	$	1,390	$	1,110	$	35	$	53	$	244	$	298
Interest cost	1,970		2,132		44		80		247		267
Expected return on plan assets	(2,950)		(2,594)		(130)		(112)		—		—
Amortization of prior service cost	109		109		—		—		—		—
Amortization of actuarial (gain) loss	484		355		(334)		(150)		211		118
Net periodic benefits costs under accounting standards	1,003		1,112		(385)		(129)		702		683
Regulatory adjustment - deferred	(121)		(160)		—		—		—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	882	$	952	$	(385)	$	(129)	$	702	$	683

	For The Nine Months Ended September 30,
	Pension Benefits				Other Postretirement Benefits				SERP
(dollars in thousands)	2020		2019		2020		2019		2020		2019
Components of Net Periodic Benefits Cost:
Service cost	$	4,170	$	3,330	$	129	$	159	$	732	$	894
Interest cost	5,910		6,396		156		240		741		801
Expected return on plan assets	(8,850)		(7,782)		(384)		(336)		—		—
Amortization of prior service cost	327		327		—		—		—		—
Amortization of actuarial (gain) loss	1,452		1,065		(732)		(450)		633		354
Net periodic benefits costs under accounting standards	3,009		3,336		(831)		(387)		2,106		2,049
Regulatory adjustment - deferred	(362)		(502)		—		—		—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	2,647	$	2,834	$	(831)	$	(387)	$	2,106	$	2,049