Retirement Benefits (Amounts Recognized on Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$ 219.2	$ 26.5
Accrued liabilities	25.6	17.9
Defined Benefit Pension Plan | U.S.
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	90.5	26.5
Accrued liabilities	19.6	10.5
Noncurrent liabilities	62.5	391.5
Net Asset (Liability) Recognized	8.4	(375.5)
Defined Benefit Pension Plan | International
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	128.7	0.0
Accrued liabilities	0.5	0.2
Noncurrent liabilities	192.8	222.7
Net Asset (Liability) Recognized	$ (64.6)	$ (222.9)