SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			4
Revenues:
Net revenues	$ 328,189	$ 107,199	$ 837,598	$ 820,952
Income (loss) from operations:
Income (loss) from operations	64,041	(20,537)	119,507	(83,367)
Capital expenditures incurred:
Capital expenditures incurred			122,816	140,921
ASSETS
Total assets	2,830,278		2,830,278		$ 2,707,188
Operating segments | Mohegan Sun
Revenues:
Net revenues	220,061	78,239	574,974	503,860
Income (loss) from operations:
Income (loss) from operations	65,183	1,692	144,195	65,951
Capital expenditures incurred:
Capital expenditures incurred			12,680	9,839
ASSETS
Total assets	1,279,799		1,279,799		1,271,435
Operating segments | Mohegan Sun Pocono
Revenues:
Net revenues	62,931	10,512	153,392	125,568
Income (loss) from operations:
Income (loss) from operations	12,319	(8,888)	20,116	(122,635)
Capital expenditures incurred:
Capital expenditures incurred			4,182	3,108
ASSETS
Total assets	406,393		406,393		409,630
Operating segments | MGE Niagara Resorts
Revenues:
Net revenues	14,380	11,346	41,193	167,602
Income (loss) from operations:
Income (loss) from operations	(11,755)	(9,778)	(35,553)	(10,163)
Capital expenditures incurred:
Capital expenditures incurred			9,654	15,330
ASSETS
Total assets	581,360		581,360		581,562
Operating segments | Management, development and other
Revenues:
Net revenues	21,782	6,546	53,691	24,012
Income (loss) from operations:
Income (loss) from operations	5,711	2,200	12,711	1,871
Capital expenditures incurred:
Capital expenditures incurred			6,974	112,161
ASSETS
Total assets	453,071		453,071		423,313
Operating segments | All other
Revenues:
Net revenues	8,362	0	10,077	0
Income (loss) from operations:
Income (loss) from operations	(1,045)	0	(499)	0
Capital expenditures incurred:
Capital expenditures incurred			89,019	0
ASSETS
Total assets	100,704		100,704		0
Corporate
Revenues:
Net revenues	162	210	2,949	438
Income (loss) from operations:
Income (loss) from operations	(6,374)	(5,749)	(21,459)	(18,360)
Capital expenditures incurred:
Capital expenditures incurred			307	483
ASSETS
Total assets	1,011,071		1,011,071		992,874
Inter-segment
Revenues:
Net revenues	511	346	1,322	(528)
Income (loss) from operations:
Income (loss) from operations	2	$ (14)	(4)	$ (31)
ASSETS
Total assets	$ (1,002,120)		$ (1,002,120)		$ (971,626)