Business Segment and Geographic Information (Reconciliation of Equity Affiliates' Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Equity affiliates' income	$ 604.3	$ 481.5	$ 294.1
Equity method investment impairment charge		(14.8)
Segment Reconciling Items
Segment Reporting Information [Line Items]
Equity method investment impairment charge	0.0	(14.8)	0.0
Segment Total
Segment Reporting Information [Line Items]
Equity affiliates' income	$ 604.3	$ 496.3	$ 294.1