Retirement Benefits (Change in Projected Benefit Obligation) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 20.9	$ 23.2	$ 39.8
Interest cost	194.9	189.8	102.8
U.S.
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at beginning of year	2,348.8	2,450.8
Service cost	9.6	10.9	18.3
Interest cost	134.9	129.9	73.9
Amendments	1.3	0.3
Actuarial loss (gain)	296.2	(68.3)
Curtailments	0.0	0.0
Settlements	(3.6)	(4.7)
Participant contributions	0.0	0.0
Benefits paid	(174.1)	(170.1)
Currency translation and other	0.0	0.0
Obligation at end of year	2,613.1	2,348.8	2,450.8
International
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at beginning of year	1,162.4	1,137.5
Service cost	11.3	12.3	21.5
Interest cost	60.0	59.9	28.9
Amendments	0.0	7.0
Actuarial loss (gain)	50.7	(80.1)
Curtailments	0.0	(14.8)
Settlements	(8.6)	(3.4)
Participant contributions	0.7	0.8
Benefits paid	(55.8)	(52.8)
Currency translation and other	118.0	96.0
Obligation at end of year	$ 1,338.7	$ 1,162.4	$ 1,137.5