Pension and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2016

Pension and Other Postretirement Benefit Expense [Abstract]

Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]

	Three Months Ended September 30,						Nine Months Ended September 30,
In thousands	2016			2015			2016			2015
Beginning balance	$	(6,825	)	$	(9,413	)	$	(7,162	)	$	(10,076	)
Amounts reclassified to AOCL	(1,795		)	—			(1,795		)	—
Amounts reclassified from AOCL:
Amortization of actuarial losses	371			549			962			1,645
Loss from plan settlement	193			—			193			—
Total reclassifications before tax	(1,231		)	549			(640		)	1,645
Tax (benefit) expense	486			(217		)	232			(650		)
Total reclassifications for the period	(745		)	332			(408		)	995
Ending balance	$	(7,570	)	$	(9,081	)	$	(7,570	)	$	(9,081	)

Schedule of Net Benefit Costs [Table Text Block]

	Three Months Ended September 30,												Nine Months Ended September 30,
	Pension Benefits						Other Postretirement Benefits						Pension Benefits						Other Postretirement Benefits
In thousands	2016			2015			2016			2015			2016			2015			2016			2015
Service cost	$	1,978		$	2,308		$	119		$	145		$	5,866		$	6,926		$	361		$	435
Interest cost	4,607			4,597			301			291			13,755			13,787			901			874
Expected return on plan assets	(5,017		)	(5,174		)	—			—			(15,051		)	(15,522		)	—			—
Amortization of net actuarial loss	3,555			4,561			192			125			10,559			13,683			575			376
Amortization of prior service costs	57			57			(117		)	50			173			173			(351		)	148
Settlement expense(1)	193			—			—			—			193			—			—			—
Net periodic benefit cost	5,373			6,349			495			611			15,495			19,047			1,486			1,833
Amount allocated to construction	(1,556		)	(2,061		)	(163		)	(218		)	(4,678		)	(5,765		)	(491		)	(607		)
Amount deferred to regulatory balancing account(2)	(1,542		)	(2,171		)	—			—			(4,762		)	(6,511		)	—			—
Net amount charged to expense	$	2,275		$	2,117		$	332		$	393		$	6,055		$	6,771		$	995		$	1,226