Short-Term and Long-Term Debt - Carrying Amount and Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2024	Sep. 30, 2024
Debt Instrument [Line Items]
Current portion of long-term debt	$ 306.0	$ 307.0
Reported Value Measurement
Debt Instrument [Line Items]
Current portion of long-term debt	306.0	307.0
Long-term debt	2,564.0	2,561.0
Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Current portion of long-term debt	305.0	305.0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Debt Instrument [Line Items]
Long-term debt	$ 2,213.0	$ 2,334.0