Debt - Total Debt (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Less: Unamortized debt issuance costs	$ (14,216)	$ (14,949)
Total	919,484	921,414
Less: Current maturities and short-term debt	(10,650)	(10,650)
Long-term debt, net of current portion	908,834	910,764
Senior secured term loan facility
Debt Instrument [Line Items]
Long-term debt	$ 933,700	$ 936,363
Senior secured term loan facility \| 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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-Name Accounting Standards Codification
-Topic 210
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- Definition

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

+ References

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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- Definition

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.

+ References

No definition available.

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- Definition

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

+ References

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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