LEASES - Cost and Accumulated Depreciation (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Lessee, Lease, Description [Line Items]
Property and equipment, net	$ 1,573,632	$ 1,498,047
Mohegan Sun
Lessee, Lease, Description [Line Items]
Property and equipment, at cost	483,788	484,143
Less: accumulated depreciation	(206,668)	(198,080)
Property and equipment, net	$ 277,120	$ 286,063

Amount, before accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(13))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant