Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

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

Details of income tax provisions and deferred income taxes from continuing operations are provided in the following tables. The components of income tax provisions and benefits were as follows:

	Year Ended December 31,
	2014			2013			2012
	(in millions)
Federal income tax provision (benefit)
Current	$	(324.0	)	$	(92.2	)	$	(10.3	)
Deferred	110.3			152.3			15.6
State income tax provision (benefit)
Current	(15.5		)	(1.4		)	(1.8		)
Deferred	(3.3		)	1.4			(5.4		)
Total income tax provision (benefit)	$	(232.5	)	$	60.1		$	(1.9	)

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

The difference between the statutory federal income tax rate and the Company's effective income tax rate is explained as follows:

	Year Ended December 31,
	2014		2013		2012
Federal income taxes statutory rate	35.0	%	35.0	%	35.0	%
Increase (decrease) in rate as a result of:
State income taxes, net of federal income tax benefit	(1.5	)%	(5.0	)%	(2,220.0	)%
State rate change	3.4	%	—	%	—	%
Penalties	—	%	0.4	%	80.0	%
Return to provision adjustment	(0.4	)%	5.0	%	1,400.0	%
Book impairment of goodwill	—	%	18.6	%	—	%
Other	(0.3	)%	(0.4	)%	325.0	%
Effective income tax rate	36.2	%	53.6	%	(380.0	)%

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

	December 31,
	2014		2013
	(in millions)
Deferred tax liabilities
Property, plant and equipment	$	1,402.9	$	1,455.6
Commodity price and interest rate derivatives	127.7		—
Total deferred tax liabilities	1,530.6		1,455.6
Deferred tax assets
Commodity price and interest rate derivatives	—		9.8
Net operating loss and tax credit carryforwards	11.7		54.4
Employee benefits and compensation costs	43.0		36.1
Accrued litigation loss contingency	—		0.8
Bonus and vacation accrual	16.3		9.0
Other	12.4		8.5
Total deferred tax assets	83.4		118.6
Net deferred income tax liability	$	1,447.2	$	1,337.0
Balance sheet classification
Deferred income tax asset - current	$	—	$	27.9
Deferred income tax liability - current	84.5		—
Deferred income tax liability - non-current	1,362.7		1,364.9
Net deferred income tax liability	$	1,447.2	$	1,337.0

Summary of Operating Loss Carryforwards [Table Text Block]

The amounts and expiration dates of net operating loss and tax credit carryforwards at December 31, 2014 are as follows:

	Expiration Dates	Amounts
		(in millions)
State net operating loss and tax credit carryforwards	2015-2033	$	30.1
State net operating loss valuation allowance		(18.4		)
U.S. alternative minimum tax credit	Indefinite	—
Total		$	11.7