Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Provision (Benefit) Charged to Continuing Operations, Accumulated Other Comprehensive Income (Loss) or Additional Paid-In Capital [Abstract]

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

Income tax expense for continuing operations consisted of the following:

	Year Ended December 31,
(dollars in millions)	2016			2015			2014
Current:
Federal	$	(14.0	)	$	9.2		$	9.3
State and local	0.5			1.7			1.9
Total current	(13.5		)	10.9			11.2
Investment tax credits	(0.1		)	(0.2		)	(0.2		)
Deferred:
Federal	72.6			149.4			69.6
State and local	5.7			5.2			1.9
Total deferred	78.3			154.6			71.5
Valuation allowance	(3.6		)	(5.5		)	(1.1		)
Total	$	61.1		$	159.8		$	81.4

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

The following is a reconciliation of the statutory federal income tax rate with the effective tax rate for each year:

	Year Ended December 31,
	2016		2015		2014
U.S. federal statutory rate	35.0	%	35.0	%	35.0	%
State and local income taxes, net of federal income tax	0.2		0.7		0.8
Change in valuation allowance, net of federal income tax	(1.4	)	(0.8	)	(2.0	)
State net operating loss adjustments	0.9		0.3		1.9
Nondeductible interest expense	—		—		2.7
Unrecognized tax benefit changes	2.3		0.2		1.4
Nondeductible compensation	0.2		0.1		0.7
Other differences, net	0.3		—		0.4
Effective tax rate	37.5	%	35.5	%	40.9	%

Schedule of income tax provision charged to continuing operations, accumulated other comprehensive income (loss) or additional paid-in capital [Table Text Block]

The income tax provision (benefit) was charged to continuing operations, discontinued operations, accumulated other comprehensive income or additional paid-in capital as follows:

	Year Ended December 31,
(dollars in millions)	2016		2015			2014
Income tax provision (benefit) related to:
Continuing operations	$	61.1	$	159.8		$	81.4
Discontinued operations	—		34.8			(24.0		)
Accumulated other comprehensive income (loss)	43.8		2.0			(22.4		)
Excess tax benefits on stock option exercises	0.1		(0.1		)	(0.1		)

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

The components of our deferred tax assets and liabilities were as follows:

	December 31,
(dollars in millions)	2016			2015
Deferred tax assets:
Net operating loss carryforwards	$	125.2		$	142.0
Pension and postretirement benefits	78.7			89.1
Investment in CyrusOne	—			68.9
Employee benefits	12.2			15.2
AMT Credit Carryforward	17.4			32.7
Texas Margin Credit	10.7			10.7
Other	19.1			17.9
Total deferred tax assets	263.3			376.5
Valuation allowance	(54.4		)	(58.4		)
Total deferred tax assets, net of valuation allowance	$	208.9		$	318.1
Deferred tax liabilities:
Property, plant and equipment	$	135.0		$	134.9
Investment in CyrusOne	9.1			—
Other	0.3			0.3
Total deferred tax liabilities	144.4			135.2
Net deferred tax assets	$	64.5		$	182.9

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

A reconciliation of the unrecognized tax benefits is as follows:

	Year Ended December 31,
(dollars in millions)	2016		2015		2014
Balance, beginning of year	$	27.6	$	27.1	$	24.1
Change in tax positions for the current year	1.2		0.5		3.0
Change in tax positions for prior years	2.6		—		—
Balance, end of year	$	31.4	$	27.6	$	27.1