SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			4
Revenues:
Net revenues	$ 278,628	$ 314,701	$ 509,409	$ 713,753
Income (loss) from operations:
Income (loss) from operations	44,856	(106,255)	55,466	(62,830)
Capital expenditures incurred:
Capital expenditures incurred			116,514	90,694
ASSETS
Total assets	2,854,191		2,854,191		$ 2,707,188
Operating segments | Mohegan Sun
Revenues:
Net revenues	189,022	182,286	354,913	425,621
Income (loss) from operations:
Income (loss) from operations	51,765	19,194	79,012	64,259
Capital expenditures incurred:
Capital expenditures incurred			8,694	7,666
ASSETS
Total assets	1,290,831		1,290,831		1,271,435
Operating segments | Mohegan Sun Pocono
Revenues:
Net revenues	52,376	53,102	90,461	115,056
Income (loss) from operations:
Income (loss) from operations	6,441	(121,541)	7,797	(113,747)
Capital expenditures incurred:
Capital expenditures incurred			2,679	2,588
ASSETS
Total assets	409,108		409,108		409,630
Operating segments | MGE Niagara Resorts
Revenues:
Net revenues	13,816	71,282	26,813	156,256
Income (loss) from operations:
Income (loss) from operations	(11,277)	948	(23,798)	(385)
Capital expenditures incurred:
Capital expenditures incurred			7,538	14,542
ASSETS
Total assets	611,408		611,408		581,562
Operating segments | Management, development and other
Revenues:
Net revenues	20,309	8,454	33,624	17,466
Income (loss) from operations:
Income (loss) from operations	5,473	589	7,546	(329)
Capital expenditures incurred:
Capital expenditures incurred			97,303	65,800
ASSETS
Total assets	555,457		555,457		423,313
Corporate
Revenues:
Net revenues	2,557	120	2,787	228
Income (loss) from operations:
Income (loss) from operations	(7,547)	(5,447)	(15,085)	(12,611)
Capital expenditures incurred:
Capital expenditures incurred			300	98
ASSETS
Total assets	987,174		987,174		992,874
Inter-segment
Revenues:
Net revenues	548	(543)	811	(874)
Income (loss) from operations:
Income (loss) from operations	1	$ 2	(6)	$ (17)
ASSETS
Total assets	$ (999,787)		$ (999,787)		$ (971,626)