Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Long-term debt, excluding capital leases
Long-term debt, excluding capital leases, Carrying Value	$ 1,600,005	$ 1,813,168
Long-term debt, excluding capital leases, Fair Value	1,655,521	1,837,104
Level 1 \| Senior notes
Long-term debt, excluding capital leases
Long-term debt, excluding capital leases, Carrying Value	1,177,380	1,177,380
Long-term debt, excluding capital leases, Fair Value	1,234,481	1,217,707
Level 2 \| Term loan B
Long-term debt, excluding capital leases
Long-term debt, excluding capital leases, Carrying Value	422,625	635,788
Long-term debt, excluding capital leases, Fair Value	421,040	619,397
Fair value measurement on recurring basis
Financial Assets:
Total assets	38	194,639
Fair value measurement on recurring basis \| Level 1 \| Cash and cash equivalents
Financial Assets:
Cash equivalents		194,612
Fair value measurement on recurring basis \| Level 2 \| Other current assets
Financial Assets:
Foreign exchange contracts	20
Fair value measurement on recurring basis \| Level 2 \| Other assets
Financial Assets:
Interest rate caps	18	$ 27
Fair value measurement on recurring basis \| Level 2 \| Accrued Liabilities
Financial Liabilities:
Foreign exchange contracts	$ 516

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value as of the balance sheet date of all foreign currency derivative assets not designated as hedging instruments.

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Fair value as of the balance sheet date of all foreign currency derivative liabilities not designated as hedging instruments.

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Fair value as of the balance sheet date of all interest rate derivative assets designated as cash flow hedging instruments.

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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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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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