Retirement Benefits - Fair Value Measurements (Details) - Non-U.S. Plans - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 259.3	$ 245.5	$ 360.3
Level 1 | Other plan assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	95.2	88.2
Level 2 | Other plan assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.3	45.3
Level 3 | Other insurance contract value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.0	2.7
Level 3 | Insurance contract - guarantee value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	82.6	75.8
Fair Value Measured at Net Asset Value Per Share | Other plan assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 29.2	$ 33.5