Retirement Benefits (Components Recognized in Accumulated Other Comprehensive Income on Pretax Basis) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
U.S.
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 461.8	$ 525.5
Prior service cost	5.6	6.5
Net transition liability	0.0	0.0
Total	467.4	532.0
International
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	506.4	511.6
Prior service cost	11.9	3.7
Net transition liability	0.4	0.4
Total	$ 518.7	$ 515.7