Retirement Benefits (Change in Projected Benefit Obligation) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 23.2	$ 39.8	$ 44.7
Interest cost	189.8	102.8	94.1
U.S.
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at beginning of year	2,450.8	3,335.3
Service cost	10.9	18.3	21.3
Interest cost	129.9	73.9	68.9
Amendments	0.3	1.5
Actuarial (gain) loss	(68.3)	(793.8)
Curtailments	0.0	0.0
Settlements	(4.7)	(19.2)
Participant contributions	0.0	0.0
Benefits paid	(170.1)	(165.2)
Currency translation and other	0.0	0.0
Obligation at end of year	2,348.8	2,450.8	3,335.3
International
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at beginning of year	1,137.5	1,969.6
Service cost	12.3	21.5	23.4
Interest cost	59.9	28.9	25.2
Amendments	7.0	0.1
Actuarial (gain) loss	(80.1)	(575.2)
Curtailments	(14.8)	0.0
Settlements	(3.4)	(0.9)
Participant contributions	0.8	1.2
Benefits paid	(52.8)	(53.0)
Currency translation and other	96.0	(254.7)
Obligation at end of year	$ 1,162.4	$ 1,137.5	$ 1,969.6