Employee Benefit Plans: (Tables)

3 Months Ended

Mar. 31, 2014

Compensation and Retirement Disclosure [Abstract]

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, before allocation to the overhead pool, for Registrant’s pension plan, postretirement plan and Supplemental Executive Retirement Plan (“SERP”) for the three months ended March 31, 2014 and 2013 are as follows:



	For The Three Months Ended March 31,
	Pension Benefits						Other Postretirement Benefits						SERP
(dollars in thousands)	2014			2013			2014			2013			2014		2013
Components of Net Periodic Benefits Cost:
Service cost	$	1,487		$	1,864		$	99		$	106		$	192	$	201
Interest cost	1,915			1,731			130			113			154		129
Expected return on plan assets	(2,215		)	(1,893		)	(113		)	(95		)	—		—
Amortization of transition	—			—			104			105			—		—
Amortization of prior service cost (benefit)	30			30			(50		)	(50		)	40		40
Amortization of actuarial (gain) loss	7			711			(66		)	—			35		85
Net periodic pension cost under accounting standards	1,224			2,443			104			179			421		455
Regulatory adjustment — deferred	300			(510		)	—			—			—		—
Total expense recognized, before allocation to overhead pool	$	1,524		$	1,933		$	104		$	179		$	421	$	455