Pensions and Other Postretirement Benefits - Pension and Postretirement Expenses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Benefits
Components of Net Periodic Cost:
Service Cost	$ 3.7	$ 3.4	$ 11.4	$ 10.7
Interest Cost	13.3	14.5	40.3	43.5
Administrative Expenses	0.3	0.2	0.7	0.5
Expected Return on Plan Assets	(18.4)	(20.8)	(55.6)	(60.8)
Net Curtailment/Settlement Gain	0.0	(0.8)	0.0	(0.8)
Amortization:
Prior Service Cost (Credit)	0.2	0.2	0.5	0.5
Actuarial Loss (Gain)	5.4	4.0	16.5	10.0
Net Periodic Cost	4.5	0.7	13.8	3.6
Postretirement Health Care Benefits
Components of Net Periodic Cost:
Service Cost	0.2	0.3	0.7	0.9
Interest Cost	0.4	0.6	1.3	1.7
Administrative Expenses	0.0	0.0	0.0	0.0
Expected Return on Plan Assets	0.0	0.0	0.0	0.0
Net Curtailment/Settlement Gain	0.0	0.0	0.0	0.0
Amortization:
Prior Service Cost (Credit)	(0.1)	(0.1)	(0.2)	(0.2)
Actuarial Loss (Gain)	(0.4)	(0.3)	(1.1)	(0.8)
Net Periodic Cost	$ 0.1	$ 0.5	$ 0.7	$ 1.6