Pension and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2015

General Discussion of Pension and Other Postretirement Benefits [Abstract]

Net Periodic Benefit Cost Components

	Nine Months Ended September 30,
							Other Postretirement
	Pension Benefits						Benefits
In thousands	2015			2014			2015			2014
Service cost	$	6,926		$	5,755		$	435		$	407
Interest cost	13,787			13,535			874			928
Expected return on plan assets	(15,522		)	(14,659		)	—			—
Amortization of net actuarial loss	13,683			7,739			376			138
Amortization of prior service costs	173			168			148			148
Net periodic benefit cost	19,047			12,538			1,833			1,621
Amount allocated to construction	(5,765		)	(3,644		)	(607		)	(518		)
Amount deferred to regulatory balancing account(1)	(6,511		)	(3,331		)	—			—
Net amount charged to expense	$	6,771		$	5,563		$	1,226		$	1,103

	Three Months Ended September 30,
							Other Postretirement
	Pension Benefits						Benefits
In thousands	2015			2014			2015			2014
Service cost	$	2,308		$	1,919		$	145		$	136
Interest cost	4,597			4,511			291			309
Expected return on plan assets	(5,174		)	(4,887		)	—			—
Amortization of net actuarial loss	4,561			2,579			125			46
Amortization of prior service costs	57			56			50			50
Net periodic benefit cost	6,349			4,178			611			541
Amount allocated to construction	(2,061		)	(1,242		)	(218		)	(177		)
Amount deferred to regulatory balancing account(1)	(2,171		)	(1,107		)	—			—
Net amount charged to expense	$	2,117		$	1,829		$	393		$	364

Schedule Of Accumulated Other Comprehensive Income Loss Rollforward [Table Text Block]

	Three Months Ended September 30,						Nine Months Ended September 30,
In thousands	2015			2014			2015			2014
Beginning balance	$	(9,413	)	$	(6,027	)	$	(10,076	)	$	(6,358	)
Amounts reclassified from AOCL:
Amortization of prior service costs	—			(1		)	—			(5		)
Amortization of actuarial losses	549			275			1,645			826
Total reclassifications before tax	549			274			1,645			821
Tax expense	(217		)	(108		)	(650		)	(324		)
Total reclassifications for the period	332			166			995			497
Ending balance	$	(9,081	)	$	(5,861	)	$	(9,081	)	$	(5,861	)