Debt (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Mar. 08, 2021
Debt Instrument [Line Items]
Total long-term debt, including current maturities		$ 1,372.0	$ 1,405.0
Long-term debt		1,360.7	1,391.4
Notes payable		$ 19.5	19.0
Notes payable, weighted-average interest rate		3.90%
Cost of early retirement of long-term debt		$ 0.0	0.0	$ 26.1
Premium for extinguishment on debt			25.5
Senior notes
Debt Instrument [Line Items]
Write off of deferred debt issuance cost			$ 0.6
Senior notes | Senior notes due 2022
Debt Instrument [Line Items]
Total long-term debt, including current maturities					$ 500.0
Debt, stated interest rate			4.70%
Senior notes | Senior notes due 2028
Debt Instrument [Line Items]
Total long-term debt, including current maturities	[1]	750.0	$ 750.0
Unamortized debt issuance costs		6.9	8.3
Senior notes | Senior Notes, Due 2029
Debt Instrument [Line Items]
Total long-term debt, including current maturities	[1]	500.0	500.0
Unamortized debt issuance costs		4.4	$ 5.3		$ 6.5
Debt, stated interest rate			4.125%
Domestic line of credit | Revolving line of credit due 2025
Debt Instrument [Line Items]
Total long-term debt, including current maturities	[2]	122.0	$ 155.0
Loans payable
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	[1]	$ 11.3	$ 13.6

[1] At September 30, 2023, the balance for the Senior Notes due 2028 and the Senior Notes due 2029 are reflected net of debt issuance costs of $6.9 and $4.4, respectively. At September 30, 2022, the balance for the Senior Notes due 2028 and the Senior Notes due 2029 are reflected net of debt issuance costs of $8.3 and $5.3, respectively.

[2] The U.S. revolving credit facility matures in 2025.