Debt Components of Long Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Total debt	$ 988.5	$ 994.3
Less debt discount	1.8	2.5
Less deferred debt costs	6.7	9.0
Less current portion of long-term debt	5.8	5.8
Long-term debt payable after one year	974.2	977.0
Term loan facility under credit agreement
Debt Instrument [Line Items]
Total debt	563.5	569.3
Line of Credit \| Revolving facility under Credit Agreement
Debt Instrument [Line Items]
Total debt	0.0	0.0
Senior Notes \| 5.500% Senior Notes due 2024
Debt Instrument [Line Items]
Total debt	$ 425.0	$ 425.0

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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Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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