Short-Term and Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2023	Sep. 30, 2023
Debt Instrument [Line Items]
Current portion of long-term debt	$ 9.9	$ 8.6
Reported Value Measurement
Debt Instrument [Line Items]
Current portion of long-term debt	9.9	8.6
Long-term debt	2,863.0	2,862.9
Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Current portion of long-term debt	9.9	8.6
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Debt Instrument [Line Items]
Long-term debt	$ 2,623.1	$ 2,442.6