SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Sep. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	4
Revenues:
Net revenues	$ 230,781	$ 399,052
Income (loss) from operations:
Income (loss) from operations	10,610	43,425
Capital expenditures incurred:
Capital expenditures incurred	15,878	36,357
ASSETS
Total assets	2,776,478		$ 2,707,188
Operating segments | Mohegan Sun
Revenues:
Net revenues	165,891	243,335
Income (loss) from operations:
Income (loss) from operations	27,247	45,065
Capital expenditures incurred:
Capital expenditures incurred	2,657	4,631
ASSETS
Total assets	1,289,586		1,271,435
Operating segments | Mohegan Sun Pocono
Revenues:
Net revenues	38,085	61,954
Income (loss) from operations:
Income (loss) from operations	1,356	7,794
Capital expenditures incurred:
Capital expenditures incurred	1,057	999
ASSETS
Total assets	404,467		409,630
Operating segments | MGE Niagara Resorts
Revenues:
Net revenues	12,997	84,974
Income (loss) from operations:
Income (loss) from operations	(12,521)	(1,333)
Capital expenditures incurred:
Capital expenditures incurred	2,560	7,851
ASSETS
Total assets	605,016		581,562
Operating segments | Management, development and other
Revenues:
Net revenues	13,315	9,012
Income (loss) from operations:
Income (loss) from operations	2,073	(918)
Capital expenditures incurred:
Capital expenditures incurred	9,306	22,868
ASSETS
Total assets	461,028		423,313
Corporate
Revenues:
Net revenues	230	108
Income (loss) from operations:
Income (loss) from operations	(7,538)	(7,164)
Capital expenditures incurred:
Capital expenditures incurred	298	8
ASSETS
Total assets	1,014,009		992,874
Inter-segment
Revenues:
Net revenues	263	(331)
Income (loss) from operations:
Income (loss) from operations	(7)	$ (19)
ASSETS
Total assets	$ (997,628)		$ (971,626)