Business Segment Information (Reconciliation of Equity Affiliates' Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Equity affiliates' income	$ 145.5	$ 143.3	$ 296.1	$ 301.7
Segment Total
Segment Reporting Information [Line Items]
Equity affiliates' income	152.3	143.3	302.9	301.7
Segment Reconciling Items | Project Exit Costs
Segment Reporting Information [Line Items]
Equity method investment impairment associated with business and asset actions	$ (6.8)	$ 0.0	$ (6.8)	$ 0.0