Pension and Other Postretirement Benefit Plans - Obligation and Funded Status (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in Plan Assets [Roll Forward]
Non-Current Liabilities		$ (177.3)	$ (191.8)
Other Postretirement Benefits Plan [Member]
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year		190.1	173.4
Service Cost		4.7	4.4	$ 3.9
Interest Cost	[1]	7.1	7.7	7.4
Plan Amendments		(2.1)	(1.8)
Actuarial (Gain) Loss		(15.8)	15.5
Benefits Paid		(11.6)	(12.2)
Participant Contributions		3.6	3.1
Obligation, End of Year		176.0	190.1	173.4
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year		171.0	154.3
Actual Return on Plan Assets		(9.6)	24.5
Employer Contribution		1.0	1.3
Defined Benefit Plan Contributions by Plan Participants, Excluding Key Employees		3.6	3.1
Benefits Paid		(11.7)	(12.2)
Fair Value, End of Year		154.3	171.0	154.3
Funded Status, End of Year		(21.7)	(19.1)
Non-Current Assets		0.4	3.0
Current Liabilities		(1.0)	(1.1)
Non-Current Liabilities		(21.1)	(21.0)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation		713.7	745.4
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year		793.2	743.3
Service Cost		11.0	10.2	8.1
Interest Cost	[2]	29.6	32.5	33.2
Plan Amendments		(1.5)	0.0
Plan Curtailments		(6.9)	0.0
Actuarial (Gain) Loss		(53.0)	44.8
Benefits Paid		(49.5)	(51.0)
Participant Contributions		24.1	13.4
Obligation, End of Year		747.0	793.2	743.3
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year		628.2	557.5
Actual Return on Plan Assets		(21.2)	91.6
Employer Contribution	[3]	40.5	30.1
Benefits Paid		(49.5)	(51.0)
Fair Value, End of Year		598.0	628.2	$ 557.5
Funded Status, End of Year		(149.0)	(165.0)
Current Liabilities		(1.6)	(1.4)
Non-Current Liabilities		$ (147.4)	$ (163.6)

[1] These components of net periodic postretirement health and life cost are included in the line item “Other” under Other Income (Expense) on the Consolidated Statement of Income.

[2] These components of net periodic pension cost are included in the line item “Other” under Other Income (Expense) on the Consolidated Statement of Income.

[3] Includes Participant Contributions noted above.