Income Tax (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

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

Dollars in thousands	2016			2015			2014
Income taxes at federal statutory rate	$	34,863		$	31,310		$	35,117
Increase (decrease):
Current state income tax, net of federal tax benefit	4,582			4,195			4,666
Amortization of investment tax credits	(41		)	(118		)	(201		)
Differences required to be flowed-through by regulatory commissions	2,357			2,357			2,357
Gains on company and trust-owned life insurance	(594		)	(766		)	(689		)
Other, net	(453		)	(1,225		)	393
Total provision for income taxes	$	40,714		$	35,753		$	41,643
Effective tax rate	40.9		%	40.0		%	41.5		%

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

In thousands	2016		2015		2014
Current
Federal	$	7,402	$	10,558	$	14,823
State	2,042		61		24
	9,444		10,619		14,847
Deferred
Federal	26,219		18,729		18,635
State	5,051		6,405		8,161
	31,270		25,134		26,796
Total provision for income taxes	$	40,714	$	35,753	$	41,643

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

In thousands	2016			2015			2014
Utility:
Current	$	10,300		$	15,890		$	24,317
Deferred	28,749			20,834			19,518
Deferred investment tax credits	(41		)	(118		)	(201		)
	39,008			36,606			43,634
Non-utility business segments:
Current	(856		)	(5,271		)	(9,470		)
Deferred	2,562			4,418			7,479
	1,706			(853		)	(1,991		)
Total provision for income taxes	$	40,714		$	35,753		$	41,643

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

In thousands	2016		2015
Deferred tax liabilities:
Plant and property	$	428,642	$	408,342
Regulatory income tax assets	43,048		47,427
Regulatory liabilities	48,291		46,400
Non-regulated deferred tax liabilities	51,446		49,683
Total	$	571,427	$	551,852
Deferred tax assets:
Pension and postretirement obligations	$	4,493	$	4,666
Alternative minimum tax credit carryforward	9,853		16,699
Loss and credit carryforwards	—		514
Total	14,346		21,879
Deferred income tax liabilities, net	557,081		529,973
Deferred investment tax credits	4		48
Deferred income taxes and investment tax credits	$	557,085	$	530,021