Debt (Details) - USD ($) $ in Millions		Dec. 31, 2021	Sep. 30, 2021
Debt Instrument [Line Items]
Total long-term debt, including current maturities		$ 1,448.0	$ 1,250.0
Long-term debt		1,432.7	1,234.2
Notes payable		27.4	26.5
Unamortized debt issuance costs	[1]	15.3	15.8
Senior notes | Senior Notes, Due 2028
Debt Instrument [Line Items]
Total long-term debt, including current maturities		750.0	750.0
Unamortized debt issuance costs		9.4	9.8
Senior notes | Senior Notes, Due 2029
Debt Instrument [Line Items]
Total long-term debt, including current maturities		500.0	500.0
Unamortized debt issuance costs		5.9	6.0
Revolving credit facility
Debt Instrument [Line Items]
Total long-term debt, including current maturities		$ 198.0	$ 0.0

[1] At December 31, 2021, the balance for the Senior Notes due 2028 and the Senior Notes due 2029 are reflected net of debt issuance costs of $9.4 and $5.9, respectively. At September 30, 2021, the balance for the Senior Notes due 2028 and the Senior Notes due 2029 are reflected net of debt issuance costs of $9.8 and $6.0, respectively.