Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Payment for Pension Benefits				$ 38.1	$ 0.0
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated pension plan contributions in current year		$ 44.1		44.1
Payment for Pension Benefits				38.1
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		60.0		60.0
Defined Benefit Plans, Estimated Future Employer Contributions, Year Two		75.0		75.0
Net periodic benefit cost (income) [Abstract]
Service cost		0.7	$ 0.8	2.1	2.1
Interest cost		27.0	31.9	81.0	95.9
Expected return on assets		(37.5)	(42.9)	(112.6)	(128.6)
Amortization of prior service cost (credit)		1.1	1.5	3.4	4.1
Amortization of (gain) loss		2.7	8.0	8.1	22.0
Settlement loss		0.0	4.9	0.0	4.9
Net periodic benefit cost (income)		(6.0)	4.2	(18.0)	0.4
Other Postretirement Benefits [Member]
Net periodic benefit cost (income) [Abstract]
Service cost		1.2	1.2	3.5	3.6
Interest cost		4.4	5.0	13.1	14.9
Amortization of prior service cost (credit)		(14.7)	(15.0)	(44.0)	(45.2)
Amortization of (gain) loss		(1.1)	(1.1)	(3.2)	(3.2)
Net periodic benefit cost (income)		$ (10.2)	$ (9.9)	$ (30.6)	$ (29.9)
Subsequent Event [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Payment for Pension Benefits	$ 6.0