Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
$500.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	$ 475.0
2020 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	400.0
2019 Notes
Liabilities:
Long-term Debt, Gross		$ 374.4
Debt Instrument, Fair Value Disclosure	374.5
$225.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	213.7
Series A Notes
Liabilities:
Long-term Debt, Gross	100.0	100.0
2010 Notes
Liabilities:
Long-term Debt, Gross		149.9
Level 1
Assets:
Cash and cash equivalents	302.2	399.0
Investments in rabbi trust	3.9	4.2
Derivative instruments	0.0	0.0
Liabilities:
Derivative instruments	0.0	0.0
Level 1 \| $500.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0
Level 1 \| 2020 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	429.0
Level 1 \| 2019 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	409.0	380.6
Level 1 \| $225.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0
Level 1 \| Series A Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0	0.0
Level 1 \| 2010 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure		152.8
Level 2
Assets:
Cash and cash equivalents	0.0	0.0
Investments in rabbi trust	0.0	0.0
Derivative instruments	2.6	2.5
Liabilities:
Derivative instruments	1.6	2.6
Level 2 \| $500.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	475.0
Level 2 \| 2020 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0
Level 2 \| 2019 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0	0.0
Level 2 \| $225.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	213.7
Level 2 \| Series A Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	105.3	108.5
Level 2 \| 2010 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure		0.0
Level 3
Assets:
Cash and cash equivalents	0.0	0.0
Investments in rabbi trust	0.0	0.0
Derivative instruments		0.0
Liabilities:
Derivative instruments	0.0	0.0
Level 3 \| $500.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0
Level 3 \| 2020 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0
Level 3 \| 2019 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0	0.0
Level 3 \| $225.0 term loan
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0
Level 3 \| Series A Notes
Liabilities:
Debt Instrument, Fair Value Disclosure	0.0	0.0
Level 3 \| 2010 Notes
Liabilities:
Debt Instrument, Fair Value Disclosure		0.0
Carrying Value
Assets:
Cash and cash equivalents	302.2	399.0
Investments in rabbi trust	3.9	4.2
Derivative instruments	2.6	2.5
Liabilities:
Derivative instruments	$ 1.6	$ 2.6

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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