Retirement Benefits (Components Recognized in Accumulated Other Comprehensive Income on Pretax Basis) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
U.S.
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 415.3	$ 461.8
Prior service cost	5.8	5.6
Net transition liability	0.0	0.0
Total	421.1	467.4
International
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	435.8	506.4
Prior service cost	11.0	11.9
Net transition liability	0.4	0.4
Total	$ 447.2	$ 518.7

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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