Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5.0	$ 5.2	$ 10.2	$ 10.4
Interest cost	43.7	48.7	87.5	97.2
Expected return on plan assets	(47.7)	(41.9)	(95.6)	(83.5)
Prior service cost amortization	0.5	0.6	1.0	1.1
Actuarial loss amortization	14.1	17.5	28.2	35.0
Settlements	0.1	0.2	0.1	0.2
Other	0.0	0.1	0.1	0.2
Net Periodic Cost	15.7	30.4	31.5	60.6
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	2.3	2.4	4.6	4.8
Interest cost	29.9	33.7	59.8	67.4
Expected return on plan assets	(33.2)	(30.0)	(66.4)	(60.0)
Prior service cost amortization	0.3	0.3	0.6	0.6
Actuarial loss amortization	11.7	14.3	23.4	28.6
Settlements	0.0	0.0	0.0	0.0
Other	0.0	0.0	0.0	0.0
Net Periodic Cost	11.0	20.7	22.0	41.4
International
Defined Benefit Plan Disclosure [Line Items]
Service cost	2.7	2.8	5.6	5.6
Interest cost	13.8	15.0	27.7	29.8
Expected return on plan assets	(14.5)	(11.9)	(29.2)	(23.5)
Prior service cost amortization	0.2	0.3	0.4	0.5
Actuarial loss amortization	2.4	3.2	4.8	6.4
Settlements	0.1	0.2	0.1	0.2
Other	0.0	0.1	0.1	0.2
Net Periodic Cost	$ 4.7	$ 9.7	$ 9.5	$ 19.2