Debt (Details) - USD ($) $ in Millions		Dec. 31, 2019	Sep. 30, 2019
Debt Instrument [Line Items]
Total long-term debt, including current maturities		$ 1,100.0	$ 1,217.0
Current maturities of long-term debt		0.0	117.0
Unamortized discount and debit issuance costs	[1],[2]	1.9	2.2
Long-term debt		1,098.1	1,097.8
Notes payable		17.0	14.4
Senior notes | Senior notes due 2021
Debt Instrument [Line Items]
Total long-term debt, including current maturities		600.0	600.0
Unamortized debt issuance costs		0.6	0.8
Senior notes | Senior notes due 2022
Debt Instrument [Line Items]
Total long-term debt, including current maturities		500.0	500.0
Unamortized debt issuance costs		1.0	1.0
Unamortized discount		0.3	0.4
Domestic line of credit
Debt Instrument [Line Items]
Total long-term debt, including current maturities		$ 0.0	$ 117.0

[1] At December 31, 2019 and September 30, 2019, the balance for the senior notes due 2022 was reflected net of discount of $0.3 and $0.4, respectively.

[2] At December 31, 2019, the balance for the senior notes due 2021 and the senior notes due 2022 are reflected net of debt issuance costs of $0.6 and $1.0, respectively. At September 30, 2019, the balance for the senior notes due 2021 and the senior notes due 2022 are reflected net of debt issuance costs of $0.8 and $1.0, respectively.