Pension and Postretirement Health and Life Benefits (Narrative) (Details) $ in Millions	3 Months Ended				6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined Benefit Plan, Net Periodic Benefit Cost								$ 26.4
Actuarial (gain) loss from remeasurement, net								29.6
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate					4.50%
Defined Contribution Plan, Cost Recognized			$ 0.9	$ 4.1				3.0
Scenario, Forecast [Member]
Expected defined benefit plan contributions for next fiscal year for non-qualified plans							$ 4.2
Expected defined benefit plan contributions for next fiscal year for postretirement health and life benefit plans							$ 5.4
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 832.8		961.4					832.8
Defined Benefit Plan, Net Periodic Benefit Cost			5.5			$ (6.2)		$ (4.5)
Approximate Number of Plan Participants	5,000							5,000
Defined Benefit Plan, Contributions by Employer			0.0			20.3		$ 8.0
Actuarial (gain) loss from remeasurement, net			$ 18.7		$ 3.9	$ 96.0		$ (55.2)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.50%	4.40%	4.10%	4.30%		4.30%		4.50%
Defined Benefit Plan, Expected Return on Plan Assets			$ 13.1			$ 38.5		$ 47.4
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost			6.1			7.0		$ 21.9
Approximate Number of Plan Participants	4,000							4,000
Defined Benefit Plan, Contributions by Employer			(0.3)			0.0		$ 0.2
Actuarial (gain) loss from remeasurement, net			$ 4.3			$ 8.3		$ (30.2)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.20%		3.80%	4.00%		4.00%		4.20%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase			2.00%	2.00%		2.00%
Defined Benefit Plan, Expected Return on Plan Assets			$ 0.4			$ 1.5		$ 0.8
Cost of Sales [Member]
Defined Benefit Plan, Net Periodic Benefit Cost								24.7
Actuarial (gain) loss from remeasurement, net	$ 48.8
Cost of Sales [Member] | Pension Plan, Defined Benefit [Member]
Actuarial (gain) loss from remeasurement, net		$ 21.6
Selling, General and Administrative Expenses [Member]
Defined Benefit Plan, Net Periodic Benefit Cost								$ 1.7
Actuarial (gain) loss from remeasurement, net	$ 1.7
Selling, General and Administrative Expenses [Member] | Pension Plan, Defined Benefit [Member]
Actuarial (gain) loss from remeasurement, net		$ 3.2