SEGMENT REPORTING (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	4
Impairment of Mohegan Sun Pocono's intangible assets	$ 126,596	$ 0	$ 0
Impairment of Mohegan Sun Pocono's goodwill	0	39,459	0
Revenues:
Revenues	1,114,962	1,388,810	1,456,980
Total	1,114,962	1,388,810	1,355,632
Income Statement [Abstract]
Income (loss) from operations:	(33,217)	136,462	244,534
Capital [Abstract]
Capital expenditures incurred	176,674	80,994	122,802
ASSETS
Total assets	2,707,188	2,511,596
Operating segments | Mohegan Sun
Revenues:
Revenues	715,674	992,043	1,068,892
Income Statement [Abstract]
Income (loss) from operations:	128,449	156,276	230,890
Capital [Abstract]
Capital expenditures incurred	17,600	30,931	93,165
ASSETS
Total assets	1,271,435	1,282,384
Operating segments | Mohegan Sun Pocono
Revenues:
Revenues	181,160	251,054	265,691
Income Statement [Abstract]
Income (loss) from operations:	(115,073)	(5,253)	37,541
Capital [Abstract]
Capital expenditures incurred	3,559	6,526	9,889
ASSETS
Total assets	409,630	548,424
Operating segments | MGE Niagara Resorts
Revenues:
Revenues	180,025	112,525	0
Income Statement [Abstract]
Income (loss) from operations:	(24,676)	7,368	0
Capital [Abstract]
Capital expenditures incurred	17,799	3,389	0
ASSETS
Total assets	581,562	342,821
Operating segments | Management, development and other
Revenues:
Revenues	37,189	33,349	19,806
Income Statement [Abstract]
Income (loss) from operations:	1,585	1,152	(686)
Capital [Abstract]
Capital expenditures incurred	137,171	40,114	19,724
ASSETS
Total assets	423,313	313,458
Corporate
Revenues:
Revenues	741	1,001	1,483
Income Statement [Abstract]
Income (loss) from operations:	(23,439)	(22,161)	(23,211)
Capital [Abstract]
Capital expenditures incurred	545	34	24
ASSETS
Total assets	992,874	912,712
Inter-segment
Revenues:
Revenues	173	(1,162)	(240)
Income Statement [Abstract]
Income (loss) from operations:	(63)	(920)	$ 0
ASSETS
Total assets	$ (971,626)	$ (888,203)