Supplemental Information (Related Party Transactions) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Related Party Transaction [Line Items]
Sales and other income	$ 70.0	$ 75.0	$ 150.0	$ 170.0
Trade receivables, net	1,845.9		1,845.9		$ 1,821.6
Current portion of long-term debt	830.7		830.7		611.4
Related Party
Related Party Transaction [Line Items]
Trade receivables, net	155.0		155.0		120.0
Total debt	294.4		294.4		304.4
Current portion of long-term debt	$ 193.5		$ 193.5		$ 200.0

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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