Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Settlements	$ (1.3)	$ (5.0)	$ (6.2)
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	21.3	23.4	21.4
Interest cost	68.9	91.2	113.4
Expected return on plan assets	(194.5)	(188.7)	(172.5)
Prior service cost amortization	1.2	1.2	1.1
Actuarial loss amortization	78.5	83.7	65.3
Settlements	1.3	5.0	6.2
Special termination benefits	0.0	0.0	0.7
Other	0.0	0.0	0.0
Net Periodic (Benefit) Cost	(23.3)	15.8	35.6
International
Defined Benefit Plan Disclosure [Line Items]
Service cost	23.4	23.3	19.3
Interest cost	25.2	24.8	35.8
Expected return on plan assets	(83.4)	(77.4)	(75.1)
Prior service cost amortization	0.0	0.0	0.0
Actuarial loss amortization	19.3	19.5	10.9
Settlements	0.5	0.2	0.2
Special termination benefits	0.0	0.0	0.1
Other	1.0	0.8	0.8
Net Periodic (Benefit) Cost	$ (14.0)	$ (8.8)	$ (8.0)