Long-Term Debt (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Sep. 30, 2024
Debt Instrument
Long-term and short-term debt, combined amount	$ 840.0		$ 840.0
Unamortized Debt Issuance Expense	(6.6)		(6.9)
Long-term debt	833.4		833.1
Revolving Credit Facility
Debt Instrument
Maximum borrowing capacity on line of credit	250.0
Repayments of lines of credit	35.0	$ 25.0
Remaining borrowing capacity on line of credit	250.0		250.0
Letters of credit outstanding, amount	0.0		$ 0.0
Proceeds from borrowing under line of credit	35.0
Letter of Credit
Debt Instrument
Maximum borrowing capacity on line of credit	$ 20.0