Retirement Benefits (Amounts Recognized on Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$ 131.7	$ 18.4
Accrued liabilities	34.1	22.6
Defined Benefit Pension Plan | U.S.
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	28.2	5.3
Accrued liabilities	23.5	12.6
Noncurrent liabilities	242.6	481.2
Net Liability Recognized	237.9	488.5
Defined Benefit Pension Plan | International
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	103.5	13.1
Accrued liabilities	1.2	0.0
Noncurrent liabilities	174.6	222.6
Net Liability Recognized	$ 72.3	$ 209.5