Retirement Benefits - Information Comparing Plan Assets to Plan Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Total
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	$ 697.7	$ 681.2
Accumulated benefit obligation	825.9	798.2
Projected benefit obligation	852.8	818.3
U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	611.6	596.3
Accumulated benefit obligation	629.2	627.2
Projected benefit obligation	629.2	627.2
Non-U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	86.1	84.9
Accumulated benefit obligation	196.7	171.0
Projected benefit obligation	$ 223.6	$ 191.1