Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Payment for Pension Benefits				$ 15.2	$ 6.0
Net periodic benefit cost (income) [Abstract]
Net periodic benefit (income) expense				(16.2)	(32.4)
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated pension plan contributions in current year		$ 49.9		49.9
Payment for Pension Benefits				15.2
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		35.0		35.0
Defined Benefit Plans, Estimated Future Employer Contributions, Year Two		10.0		10.0
Net periodic benefit cost (income) [Abstract]
Service cost		0.7	$ 0.7	1.5	1.4
Interest cost		23.8	27.0	47.5	54.0
Expected return on assets		(38.8)	(37.5)	(77.6)	(75.1)
Amortization of prior service cost (credit)		0.9	1.1	1.9	2.3
Amortization of (gain) loss		4.0	2.7	7.9	5.4
Net periodic benefit (income) expense		(9.4)	(6.0)	(18.8)	(12.0)
Other Postretirement Benefits [Member]
Net periodic benefit cost (income) [Abstract]
Service cost		1.2	1.1	2.3	2.3
Interest cost		3.9	4.4	7.8	8.7
Amortization of prior service cost (credit)		(3.4)	(14.7)	(6.8)	(29.3)
Amortization of (gain) loss		(0.4)	(1.0)	(0.7)	(2.1)
Net periodic benefit (income) expense		$ 1.3	$ (10.2)	$ 2.6	$ (20.4)
Subsequent Event [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Payment for Pension Benefits	$ 9.2