Income Tax (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

Dollars in thousands	2015			2014			2013
Income taxes at federal statutory rate	$	31,310		$	35,117		$	35,785
Increase (decrease):
Current state income tax, net of federal tax benefit	4,195			4,666			4,674
Amortization of investment tax credits	(118		)	(201		)	(271		)
Differences required to be flowed-through by regulatory commissions	2,357			2,357			2,357
Gains on company and trust-owned life insurance	(766		)	(689		)	(864		)
Other, net	(1,225		)	393			24
Total provision for income taxes	$	35,753		$	41,643		$	41,705
Effective tax rate	40.0		%	41.5		%	40.8		%

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

In thousands	2015		2014		2013
Current
Federal	$	10,558	$	14,823	$	(62	)
State	61		24		(11		)
	10,619		14,847		(73		)
Deferred
Federal	18,729		18,635		35,109
State	6,405		8,161		6,669
	25,134		26,796		41,778
Total provision for income taxes	$	35,753	$	41,643	$	41,705

Schedule Of Regulated Utility And Non Utility Business Segments [Table Text Block]

In thousands	2015			2014			2013
Utility:
Current	$	15,890		$	24,317		$	(73	)
Deferred	20,834			19,518			38,073
Deferred investment tax credits	(118		)	(201		)	(271		)
	36,606			43,634			37,729
Non-utility business segments:
Current	(5,271		)	(9,470		)	—
Deferred	4,418			7,479			3,976
	(853		)	(1,991		)	3,976
Total provision for income taxes	$	35,753		$	41,643		$	41,705

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

In thousands	2015		2014
Deferred tax liabilities:
Plant and property	$	408,342	$	386,732
Regulatory income tax assets	47,427		51,805
Regulatory liabilities	46,400		55,776
Non-regulated deferred tax liabilities	49,683		48,683
Total	$	551,852	$	542,996
Deferred tax assets:
Pension and postretirement obligations	$	4,666	$	6,537
Alternative minimum tax credit carryforward	16,699		16,788
Loss and credit carryforwards	514		12,657
Total	21,879		35,982
Deferred income tax liabilities, net	529,973		507,014
Deferred investment tax credits	48		166
Deferred income taxes and investment tax credits	$	530,021	$	507,180