Pension and Other Postretirement Benefit Plans - Obligation and Funded Status (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in Plan Assets [Roll Forward]
Non-Current Liabilities		$ (172.8)	$ (177.3)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Loss	[1]	(16.0)	(25.0)
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year		176.0	190.1
Service Cost		3.9	4.7	$ 4.4
Interest Cost	[2]	7.3	7.1	7.7
Plan Amendments	[3]	(34.6)	(2.1)
Actuarial (Gain) Loss		10.5	(15.8)
Benefits Paid		(14.7)	(11.6)
Participant Contributions		3.5	3.6
Obligation, End of Year		149.8	176.0	190.1
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year		154.3	171.0
Actual Return on Plan Assets		29.5	(9.6)
Employer Contribution		1.1	1.0
Defined Benefit Plan Contributions by Plan Participants, Excluding Key Employees		3.5	3.6
Benefits Paid		(14.7)	(11.7)
Fair Value, End of Year		173.7	154.3	171.0
Funded Status, End of Year		23.9	(21.7)
Non-Current Assets		37.5	0.4
Current Liabilities		(0.7)	(1.0)
Non-Current Liabilities		(12.9)	(21.1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]	(2.1)	0.0	0.0
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Loss		(243.4)	(230.5)
Accumulated Benefit Obligation		812.0	713.7
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year		747.0	793.2
Service Cost		9.3	11.0	10.2
Interest Cost	[4]	31.9	29.6	32.5
Plan Amendments		0.0	(1.5)
Plan Curtailments		0.0	(6.9)
Actuarial (Gain) Loss		98.3	(53.0)
Benefits Paid		(53.4)	(49.5)
Participant Contributions		20.9	24.1
Obligation, End of Year		854.0	747.0	793.2
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year		598.0	628.2
Actual Return on Plan Assets		122.1	(21.2)
Employer Contribution	[5]	32.9	40.5
Benefits Paid		(53.4)	(49.5)
Fair Value, End of Year		699.6	598.0	$ 628.2
Funded Status, End of Year		(154.4)	(149.0)
Current Liabilities		(1.6)	(1.6)
Non-Current Liabilities		$ (152.8)	$ (147.4)

[1] Excludes gains, losses and contributions associated with irrevocable grantor trusts.

[2] 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.

[3] Plan design changes under the other postretirement benefit plans resulted in a decrease to the benefit obligation of $34.6 million in 2019.

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

[5] Includes Participant Contributions noted above.