Debt - Total Debt (Details) - USD ($) $ in Thousands	6 Months Ended
Mar. 31, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Less: Unamortized debt issuance costs	$ (10,585)	$ (12,031)
Total	909,803	916,344
Less: Current maturities and short-term debt	(10,650)	(13,313)
Long-term debt, net of current portion	899,153	903,031
Senior secured term loan facility
Debt Instrument [Line Items]
Long-term debt	$ 920,388	$ 928,375
Senior secured term loan facility \| LIBOR \| Credit Agreement
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. 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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