Pension and Postretirement Health and Life Benefits Pension and Postretirement Health and Life Benefits (Schedule of Changes in Projected Benefit Obligations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
Dec. 31, 2014	Jun. 30, 2013	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Benefit Obligation	$ 961.4		$ 965.1	$ 907.4	$ 1,099.0
Defined Benefit Plan, Actuarial Gain (Loss)	18.7		96.0	(121.0)
Defined Benefit Plan, Service Cost	2.0		1.8	9.9
Defined Benefit Plan, Interest Cost	10.2		31.7	45.0
Defined Benefit Plan, Benefits Paid	(15.0)		(44.3)	(58.2)
Defined Benefit Plan, Lump Sum Benefits Paid	(17.9)		(24.7)	(47.2)
Defined Benefit Plan, Gross Prescription Drug Subsidy Receipts Received	0		0	0
Defined Benefit Plan, Plan Amendments	0		0	0
Defined Benefit Plan, Curtailments	0	32.7	(2.8)	(20.1)
Defined Benefit Plan, Special Termination Benefits	0		0	0
Defined Benefit Plan, Fair Value of Plan Assets	772.4		781.5	784.0	774.8
Defined Benefit Plan, Actual Return on Plan Assets	25.5		46.2	92.7
Defined Benefit Plan, Contributions by Employer	0		20.3	21.9
Defined Benefit Plan, Funded Status of Plan	(189.0)		(183.6)	(123.4)
Amounts Recognized In Current Liabilities	(9.7)		(9.5)	(2.2)
Amounts Recognized In Noncurrent Liabilities	(179.3)		(174.1)	(121.2)
Defined Benefit Plan, Amounts Recognized in Balance Sheet	(189.0)		(183.6)	(123.4)
Amounts Recognized In Accumulated Other Comprehensive Income Pre Tax Net Actuarial Loss	0		202.4	115.3
Recognized In Accumulated Other Comprehensive Income Pre Tax Prior Service Cost Credit	0		0	0.2
AmountsRecognizedInAccumulatedOtherComprehensiveIncomePreTax	0		202.4	115.5
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.10%		4.30%	4.90%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase				2.00%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Benefit Obligation	237.7		240.4	231.9	248.8
Defined Benefit Plan, Actuarial Gain (Loss)	4.3		8.3	(25.2)
Defined Benefit Plan, Service Cost	0.2		1.3	3.6
Defined Benefit Plan, Interest Cost	2.3		7.5	9.0
Defined Benefit Plan, Benefits Paid	(2.8)		(8.7)	(12.2)
Defined Benefit Plan, Lump Sum Benefits Paid	0		0	0
Defined Benefit Plan, Gross Prescription Drug Subsidy Receipts Received	0.1		0.1	0.5
Defined Benefit Plan, Plan Amendments	(6.8)		0	(27.8)
Defined Benefit Plan, Curtailments	0		0	24.6
Defined Benefit Plan, Special Termination Benefits	0		0	10.6
Defined Benefit Plan, Fair Value of Plan Assets	26.3		28.7	36.9	41.6
Defined Benefit Plan, Actual Return on Plan Assets	0.7		0.5	6.9
Defined Benefit Plan, Contributions by Employer	(0.3)		0	0.6
Defined Benefit Plan, Funded Status of Plan	(211.4)		(211.7)	(195.0)
Amounts Recognized In Current Liabilities	0		0	0
Amounts Recognized In Noncurrent Liabilities	(211.4)		(211.7)	(195.0)
Defined Benefit Plan, Amounts Recognized in Balance Sheet	(211.4)		(211.7)	(195.0)
Amounts Recognized In Accumulated Other Comprehensive Income Pre Tax Net Actuarial Loss	0		22.0	12.8
Recognized In Accumulated Other Comprehensive Income Pre Tax Prior Service Cost Credit	(6.8)		(1.8)	(2.1)
AmountsRecognizedInAccumulatedOtherComprehensiveIncomePreTax	$ (6.8)		$ 20.2	$ 10.7
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.80%		4.00%	4.50%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	2.00%		2.00%	2.00%

Pension and Postretirement Health and Life Benefits Pension and Postretirement Health and Life Benefits (Schedule of Changes in Projected Benefit Obligations) (Details) (USD $)
In Millions, unless otherwise specified