Derivative Financial Instruments and Fair Value Measurements - Schedule of Financial Assets and Liabilities Recorded at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Millions	Dec. 31, 2024	Sep. 30, 2024
Derivative [Line Items]
Other current assets	$ 10.5	$ 9.2
Other non-current assets	23.3	16.5
Other current liabilities	(0.3)	(0.9)
Other long-term liabilities		(3.6)
Credit facility investment	6.2	21.9
Equity investment	24.4	19.4
Total net assets at fair value	64.1	62.5
Quoted Prices in Active Markets for Identical Assets (Level 1)
Derivative [Line Items]
Other current assets	0.0	0.0
Other non-current assets	0.0	0.0
Other current liabilities	0.0	0.0
Other long-term liabilities		0.0
Credit facility investment	0.0	0.0
Equity investment	24.4	19.4
Total net assets at fair value	24.4	19.4
Significant Observable Inputs (Level 2)
Derivative [Line Items]
Other current assets	10.5	9.2
Other non-current assets	23.3	16.5
Other current liabilities	(0.3)	(0.9)
Other long-term liabilities		(3.6)
Credit facility investment	0.0	0.0
Equity investment	0.0	0.0
Total net assets at fair value	33.5	21.2
Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Other current assets	0.0	0.0
Other non-current assets	0.0	0.0
Other current liabilities	0.0	0.0
Other long-term liabilities		0.0
Credit facility investment	6.2	21.9
Equity investment	0.0	0.0
Total net assets at fair value	$ 6.2	$ 21.9