Retirement Benefits - Information Comparing Plan Assets to Plan Obligations (Details) $ in Millions		3 Months Ended	12 Months Ended
	Oct. 08, 2019 USD ($) participant	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Total
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets		$ 750.1	$ 750.1	$ 731.5
Accumulated benefit obligation		951.0	951.0	906.5
Projected benefit obligation		968.9	968.9	921.6
Primary U.S. Pension Plan Obligation Settled			54.5	0.0
Settlement charge			(21.4)	(1.7)	$ (2.0)
U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets		699.3	699.3	686.6
Accumulated benefit obligation		826.8	826.8	801.9
Projected benefit obligation		826.8	826.8	801.9
Primary U.S. Pension Plan Obligation Settled			53.6	0.0
Settlement charge			(19.3)	0.0	0.0
U.S. Plans | Total
Information for pension plans with an ABO in excess of plan assets:
Annuity Buy Out Number of Participants | participant	2,600
Plan asset payment for settlement	$ 53.0
Primary U.S. Pension Plan Obligation Settled	$ 54.0
Settlement charge		19.3
Non-U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets		50.8	50.8	44.9
Accumulated benefit obligation		124.2	124.2	104.6
Projected benefit obligation		$ 142.1	142.1	119.7
Primary U.S. Pension Plan Obligation Settled			0.9	0.0
Settlement charge			$ (2.1)	$ (1.7)	$ (2.0)