SEGMENT REPORTING (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	4
Impairment of Mohegan Sun Pocono's intangible assets	$ 0	$ 126,596	$ 0
Impairment of Mohegan Sun Pocono's goodwill	0	0	39,459
Revenues:
Total	1,228,833	1,114,962	1,388,810
Income (loss) from operations:
Income (loss) from operations	184,457	(33,217)	136,462
Capital expenditures incurred:
Capital expenditures incurred	140,197	176,674	80,994
ASSETS
Total assets	2,729,877	2,707,188
Operating segments | Mohegan Sun
Revenues:
Revenues	816,376	715,674	992,043
Income (loss) from operations:
Income (loss) from operations	202,311	128,449	156,276
Capital expenditures incurred:
Capital expenditures incurred	23,250	17,600	30,931
ASSETS
Total assets	1,267,538	1,271,435
Operating segments | Mohegan Sun Pocono
Revenues:
Revenues	221,479	181,160	251,054
Income (loss) from operations:
Income (loss) from operations	32,534	(115,073)	(5,253)
Capital expenditures incurred:
Capital expenditures incurred	6,063	3,559	6,526
ASSETS
Total assets	408,187	409,630
Operating segments | MGE Niagara Resorts
Revenues:
Revenues	99,202	180,025	112,525
Income (loss) from operations:
Income (loss) from operations	(22,638)	(24,676)	7,368
Capital expenditures incurred:
Capital expenditures incurred	14,079	17,799	3,389
ASSETS
Total assets	561,812	581,562
Operating segments | Management, development and other
Revenues:
Revenues	70,009	37,189	33,349
Income (loss) from operations:
Income (loss) from operations	17,162	1,585	1,152
Capital expenditures incurred:
Capital expenditures incurred	7,773	137,171	40,114
ASSETS
Total assets	407,831	423,313
Operating segments | All other
Revenues:
Revenues	18,780	0	0
Income (loss) from operations:
Income (loss) from operations	(1,534)	0	0
Capital expenditures incurred:
Capital expenditures incurred	88,725	0	0
ASSETS
Total assets	98,945	0
Corporate
Revenues:
Revenues	3,247	741	1,001
Income (loss) from operations:
Income (loss) from operations	(43,358)	(23,439)	(22,161)
Capital expenditures incurred:
Capital expenditures incurred	307	545	34
ASSETS
Total assets	996,040	992,874
Inter-segment
Revenues:
Revenues	(260)	173	(1,162)
Income (loss) from operations:
Income (loss) from operations	(20)	(63)	$ (920)
ASSETS
Total assets	$ (1,010,476)	$ (971,626)