Supplemental Information (Related Party Transactions) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Sep. 30, 2025
Related Party Transaction [Line Items]
Sales and other income	$ 85.0	$ 80.0
Trade receivables, net	1,894.9		$ 1,901.2
Current portion of long-term debt	169.8		716.3
Related Party
Related Party Transaction [Line Items]
Trade receivables, net	160.0		105.0
Current portion of long-term debt	60.0		59.0
Related Party | Lu-An Clean Energy Company Transaction
Related Party Transaction [Line Items]
Total debt	$ 240.7		$ 236.5