Supplemental Information (Related Party Transactions) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Related Party Transaction [Line Items]
Sales and other income	$ 105.0	$ 70.0	$ 190.0	$ 150.0
Trade receivables, net	1,937.7		1,937.7		$ 1,901.2
Current portion of long-term debt	173.5		173.5		716.3
Related Party
Related Party Transaction [Line Items]
Trade receivables, net	205.0		205.0		105.0
Current portion of long-term debt	61.0		61.0		59.0
Related Party | Lu-An Clean Energy Company Transaction
Related Party Transaction [Line Items]
Total debt	$ 244.3		$ 244.3		$ 236.5