Segment Reporting - Financial Information Related to Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Revenues:
Net revenues	$ 314,701	$ 307,697	$ 713,753	$ 627,197
Income Statement [Abstract]
Income (loss) from operations	(106,255)	22,226	(62,830)	65,596
Capital [Abstract]
Capital expenditures incurred			90,694	38,425
ASSETS
Total assets	2,717,242	2,511,596	2,717,242	2,511,596	$ 2,511,596
Operating Segments | Mohegan Sun
Revenues:
Net revenues	182,286	238,391	425,621	491,070
Income Statement [Abstract]
Income (loss) from operations	19,194	19,913	64,259	63,976
Capital [Abstract]
Capital expenditures incurred			7,666	17,101
ASSETS
Total assets	1,278,400	1,282,384	1,278,400	1,282,384
Operating Segments | Mohegan Sun Pocono
Revenues:
Net revenues	53,102	61,241	115,056	122,032
Income Statement [Abstract]
Income (loss) from operations	(121,541)	8,214	(113,747)	15,406
Capital [Abstract]
Capital expenditures incurred			2,588	1,631
ASSETS
Total assets	395,327	548,424	395,327	548,424
Operating Segments | M G E Niagara Resorts
Revenues:
Net revenues	71,282		156,256
Income Statement [Abstract]
Income (loss) from operations	948		(385)
Capital [Abstract]
Capital expenditures incurred			14,542
ASSETS
Total assets	508,754	342,821	508,754	342,821
Operating Segments | Management, Development and Other
Revenues:
Net revenues	8,454	7,837	17,466	13,549
Income Statement [Abstract]
Income (loss) from operations	589	754	(329)	341
Capital [Abstract]
Capital expenditures incurred			65,800	19,665
ASSETS
Total assets	421,497	313,458	421,497	313,458
Corporate
Revenues:
Net revenues	120	288	228	666
Income Statement [Abstract]
Income (loss) from operations	(5,447)	(6,655)	(12,611)	(14,127)
Capital [Abstract]
Capital expenditures incurred			98	28
ASSETS
Total assets	1,061,890	912,712	1,061,890	912,712
Inter-segment
Revenues:
Net revenues	(543)	(60)	(874)	(120)
Income Statement [Abstract]
Income (loss) from operations	2		(17)
ASSETS
Total assets	$ (948,626)	$ (888,203)	$ (948,626)	$ (888,203)