Retirement Benefits (Amounts Recognized on Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$ 26.5	$ 28.7
Accrued liabilities	17.9	26.0
Defined Benefit Pension Plan | U.S.
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	26.5	17.3
Accrued liabilities	10.5	18.3
Noncurrent liabilities	391.5	448.2
Net Liability Recognized	375.5	449.2
Defined Benefit Pension Plan | International
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	0.0	11.4
Accrued liabilities	0.2	0.0
Noncurrent liabilities	222.7	203.0
Net Liability Recognized	$ 222.9	$ 191.6