Fair Value of Financial Instruments (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Assets:
Cash and cash equivalents	$ 278,895	$ 257,354
Other long-term investments	1,282	1,214
Derivative financial instruments	289	27
Liabilities:
Derivative financial instruments	6,734	38,157
Level 1
Assets:
Cash and cash equivalents	278,895	257,354
Other long-term investments	1,282	1,214
Derivative financial instruments	0	0
Liabilities:
Derivative financial instruments	0	0
Level 2
Assets:
Cash and cash equivalents	0	0
Other long-term investments	0	0
Derivative financial instruments	289	27
Liabilities:
Derivative financial instruments	6,734	38,157
Level 3
Assets:
Cash and cash equivalents	0	0
Other long-term investments	0	0
Derivative financial instruments	0	0
Liabilities:
Derivative financial instruments	$ 0	$ 0

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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, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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