Leases - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease cost	$ 19,551	$ 23,624
Finance lease, depreciation of lease assets	175	2,078
Finance lease, interest on lease liabilities	11	186
Short-term lease cost	85	1,171
Variable lease cost	1,190	3,264
Total lease cost	$ 21,012	$ 30,323
Operating Lease, weighted average remaining lease term	53 months	63 months
Finance lease, weighted average remaining lease term	0 months	29 months
Operating lease, weighted average discount rate	3.64%	3.86%
Finance lease, weighted average discount rate	0.00%	2.56%

Amount of interest expense on finance lease liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

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Weighted average discount rate for finance lease calculated at point in time.

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Weighted average remaining lease term for finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Amount of lease cost recognized by lessee for lease contract.

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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

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Weighted average discount rate for operating lease calculated at point in time.

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Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

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