Business Segment and Geographic Information (Reconciliation of Operating Income) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Facility closure	$ (23.2)	$ 0.0	$ 0.0	$ (23.2)
Business and asset actions		(244.6)	(73.7)	0.0
Gain on exchange with joint venture partner		0.0	0.0	36.8
Operating income		2,494.6	2,338.8	2,281.4
Segment Reconciling Items
Segment Reporting Information [Line Items]
Facility closure		0.0	0.0	(23.2)
Business and asset actions		(244.6)	(73.7)	0.0
Gain on exchange with joint venture partner		0.0	0.0	36.8
Segment Total
Segment Reporting Information [Line Items]
Operating income		$ 2,739.2	$ 2,412.5	$ 2,267.8