Income Tax (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

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

Dollars in thousands	2017			2016			2015
Income taxes (benefits) at federal statutory rate	$	(30,233	)	$	34,863		$	31,310
Increase (decrease):
State income tax, net of federal	(5,784		)	4,582			4,195
Amortization of investment tax credits	(4		)	(41		)	(118		)
Differences required to be flowed-through by regulatory commissions	2,357			2,357			2,357
Gains on company and trust-owned life insurance	(872		)	(594		)	(766		)
Effect of TCJA	(21,429		)	—			—
Deferred Tax Rate Differential Post-TCJA	26,947			—			—
Other, net	(1,739		)	(453		)	(1,225		)
Total provision for income taxes (benefits)	$	(30,757	)	$	40,714		$	35,753
Effective tax rate	35.6		%	40.9		%	40.0		%

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

In thousands	2017			2016		2015
Current
Federal	$	16,403		$	7,402	$	10,558
State	4,892			2,042		61
	21,295			9,444		10,619
Deferred
Federal	(41,134		)	26,219		18,729
State	(10,918		)	5,051		6,405
	(52,052		)	31,270		25,134
Total provision for income taxes (loss benefits)	$	(30,757	)	$	40,714	$	35,753

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

In thousands	2017			2016			2015
Utility:
Current	$	21,453		$	10,300		$	15,890
Deferred	19,479			28,749			20,834
Deferred investment tax credits	(4		)	(41		)	(118		)
	40,928			39,008			36,606
Non-utility business segments:
Current	(158		)	(856		)	(5,271		)
Deferred	(71,527		)	2,562			4,418
	(71,685		)	1,706			(853		)
Total provision for income taxes	$	(30,757	)	$	40,714		$	35,753

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

In thousands	2017		2016
Deferred tax liabilities:
Plant and property	$	296,114	$	428,642
Regulatory income tax assets	22,209		43,048
Regulatory liabilities	29,114		48,291
Non-regulated deferred tax liabilities	933		51,446
Total	$	348,370	$	571,427
Deferred tax assets:
Regulatory income tax liabilities	$	56,470	$	—
Non-regulated deferred tax assets	17,796		—
Pension and postretirement obligations	3,512		4,493
Alternative minimum tax credit carryforward	66		9,853
Total	$	77,844	$	14,346
Deferred income tax liabilities, net	$	270,526	$	557,081
Deferred investment tax credits	—		4
Deferred income taxes and investment tax credits	$	270,526	$	557,085