Employee Benefit Plans: (Tables)

6 Months Ended

Jun. 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 six months ended June 30, 2020 and 2019 were as follows:



	For The Three Months Ended June 30,
	Pension Benefits						Other Postretirement Benefits						SERP
(dollars in thousands)	2020			2019			2020			2019			2020		2019
Components of Net Periodic Benefits Cost:
Service cost	$	1,372		$	986		$	47		$	53		$	244	$	298
Interest cost	1,986			2,133			56			80			247		267
Expected return on plan assets	(2,950		)	(2,595		)	(127		)	(112		)	—		—
Amortization of prior service cost	109			109			—			—			—		—
Amortization of actuarial (gain) loss	526			351			(199		)	(150		)	211		118
Net periodic benefits costs under accounting standards	1,043			984			(223		)	(129		)	702		683
Regulatory adjustment - deferred	(148		)	(342		)	—			—			—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	895		$	642		$	(223	)	$	(129	)	$	702	$	683

	For The Six Months Ended June 30,
	Pension Benefits						Other Postretirement Benefits						SERP
(dollars in thousands)	2020			2019			2020			2019			2020		2019
Components of Net Periodic Benefits Cost:
Service cost	$	2,780		$	2,220		$	94		$	106		$	488	$	596
Interest cost	3,940			4,264			112			160			494		534
Expected return on plan assets	(5,900		)	(5,188		)	(254		)	(224		)	—		—
Amortization of prior service cost	218			218			—			—			—		—
Amortization of actuarial (gain) loss	968			710			(398		)	(300		)	422		236
Net periodic benefits costs under accounting standards	2,006			2,224			(446		)	(258		)	1,404		1,366
Regulatory adjustment - deferred	(241		)	(342		)	—			—			—		—
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$	1,765		$	1,882		$	(446	)	$	(258	)	$	1,404	$	1,366