Retirement Benefits (Details 4) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Termination benefits	$ 17.4	$ 17.4
Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year		2,633.9	$ 2,497.7
Service cost		12.7	12.7	$ 16.4
Interest cost		86.3	105.5	104.8
Benefits paid		(258.0)	(274.6)
Subsidy paid		0.0	0.0
Effect of currency rates		4.3	2.8
Net actuarial (gains) losses - discount rate change		235.3	266.0
Net actuarial (gains) losses - other		(5.3)	14.3
Plan curtailments		0.0	0.0
Plan amendments		0.0	9.5
Termination benefits		10.9	0.0	0.0
Benefit obligation at end of year	2,720.1	2,720.1	2,633.9	2,497.7
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year		345.3	359.1
Service cost		2.3	1.9	2.5
Interest cost		10.7	14.8	12.7
Benefits paid		(30.4)	(37.7)
Subsidy paid		0.8	0.0
Effect of currency rates		0.0	0.0
Net actuarial (gains) losses - discount rate change		25.5	30.5
Net actuarial (gains) losses - other		(0.8)	(18.1)
Plan curtailments		(2.5)	0.0
Plan amendments		0.0	(5.2)
Termination benefits		6.7	0.0	0.0
Benefit obligation at end of year	$ 357.6	$ 357.6	$ 345.3	$ 359.1