Retirement Benefits (Change in Projected Benefit Obligation) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 20.7	$ 20.9	$ 23.2
Interest cost	176.5	194.9	189.8
U.S.
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at beginning of year	2,613.1	2,348.8
Service cost	9.1	9.6	10.9
Interest cost	119.5	134.9	129.9
Amendments	0.3	1.3
Actuarial (gain) loss	(44.7)	296.2
Curtailments	1.2	0.0
Settlements	(3.0)	(3.6)
Participant contributions	0.0	0.0
Benefits paid	(179.8)	(174.1)
Currency translation and other	0.0	0.0
Obligation at end of year	2,515.7	2,613.1	2,348.8
International
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at beginning of year	1,338.7	1,162.4
Service cost	11.6	11.3	12.3
Interest cost	57.0	60.0	59.9
Amendments	0.0	0.0
Actuarial (gain) loss	(88.7)	50.7
Curtailments	0.0	0.0
Settlements	(6.0)	(8.6)
Participant contributions	0.7	0.7
Benefits paid	(59.7)	(55.8)
Currency translation and other	26.0	118.0
Obligation at end of year	$ 1,279.6	$ 1,338.7	$ 1,162.4