Retirement Benefits (Components Recognized in Accumulated Other Comprehensive Income on Pretax Basis) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
U.S.
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 797.7	$ 871.8
Prior service cost (credit)	7.0	6.6
Net transition liability	0.0	0.0
Total	804.7	878.4
International
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	643.2	594.0
Prior service cost (credit)	3.6	3.6
Net transition liability	0.4	0.4
Total	$ 647.2	$ 598.0

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

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