Pension and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2015

General Discussion of Pension and Other Postretirement Benefits [Abstract]

Net Periodic Benefit Cost Components

	Six Months Ended June 30,
							Other Postretirement
	Pension Benefits						Benefits
In thousands	2015			2014			2015			2014
Service cost	$	4,618		$	3,836		$	290		$	271
Interest cost	9,190			9,024			583			619
Expected return on plan assets	(10,348		)	(9,772		)	—			—
Amortization of net actuarial loss	9,122			5,160			251			92
Amortization of prior service costs	116			112			98			98
Net periodic benefit cost	12,698			8,360			1,222			1,080
Amount allocated to construction	(3,704		)	(2,402		)	(389		)	(341		)
Amount deferred to regulatory balancing account(1)	(4,340		)	(2,224		)	—			—
Net amount charged to expense	$	4,654		$	3,734		$	833		$	739

	Three Months Ended June 30,
							Other Postretirement
	Pension Benefits						Benefits
In thousands	2015			2014			2015			2014
Service cost	$	2,309		$	1,918		$	145		$	136
Interest cost	4,595			4,512			292			309
Expected return on plan assets	(5,174		)	(4,886		)	—			—
Amortization of net actuarial loss	4,561			2,580			125			46
Amortization of prior service costs	58			56			49			49
Net periodic benefit cost	6,349			4,180			611			540
Amount allocated to construction	(1,879		)	(1,201		)	(198		)	(171		)
Amount deferred to regulatory balancing account(1)	(2,165		)	(1,123		)	—			—
Net amount charged to expense	$	2,305		$	1,856		$	413		$	369

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

	Three Months Ended June 30,						Six Months Ended June 30,
In thousands	2015			2014			2015			2014
Beginning balance	$	(9,744	)	$	(6,193	)	$	(10,076	)	$	(6,358	)
Amounts reclassified from AOCL:
Amortization of prior service costs	—			(2		)	—			(4		)
Amortization of actuarial losses	548			276			1,096			551
Total reclassifications before tax	548			274			1,096			547
Tax expense	(217		)	(108		)	(433		)	(216		)
Total reclassifications for the period	331			166			663			331
Ending balance	$	(9,413	)	$	(6,027	)	$	(9,413	)	$	(6,027	)