Retirement Benefits (Components Recognized in Accumulated Other Comprehensive Income on Pretax Basis) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
U.S.
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 403.5	$ 415.3
Prior service cost	5.0	5.8
Net transition liability	0.0	0.0
Total	408.5	421.1
International
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	428.0	435.8
Prior service cost	10.0	11.0
Net transition liability	0.4	0.4
Total	$ 438.4	$ 447.2