SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES - Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 188,663	$ 917,534	$ 370,553	$ 487,884
Restricted cash	33,900	19,200	51,300	48,900
Total cash, cash equivalents, and restricted cash	222,589	936,716	421,872	536,747
Prepaid expenses and other, net
Summary of Significant Accounting Policies [Line Items]
Restricted cash	33,242	18,350	48,434	45,577
Other assets, net
Summary of Significant Accounting Policies [Line Items]
Restricted cash	$ 684	$ 832	$ 2,885	$ 3,286

Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, 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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(2))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.5-02(1))
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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Name:	us-gaap_RestrictedCashAndCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant