CONSOLIDATED STATEMENTS OF CHANGES IN CAPITAL - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member		us-gaap:AccountingStandardsUpdate201409Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period	$ 137,433	$ 270,794	$ 309,169
Net income (loss)	(162,016)	(2,376)	131,608
Foreign currency translation adjustment	7,303	(18,666)	9,362
Contribution from Mohegan Tribe	10,000
Distributions to Mohegan Tribe	(60,000)	(60,000)	(60,000)
Ownership rights settlement related to Project Inspire			(6,147)
Redemption of membership interest related to Project Inspire			(106,702)
Redemption of Mohegan Tribe membership interest related to the Cowlitz Project		(10,000)
Redemption of membership interest related to the New England Black Wolves franchise		75
Other	(48)	31
Total capital at end of period	(67,989)	137,433	270,794
Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period		(41,575)
Total capital at end of period			(41,575)
Retained Earnings (Deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period	137,124	250,707	196,645
Net income (loss)	(162,155)	(2,545)	130,554
Contribution from Mohegan Tribe	10,000
Distributions to Mohegan Tribe	(60,000)	(60,000)	(60,000)
Redemption of membership interest related to Project Inspire			(9,996)
Redemption of Mohegan Tribe membership interest related to the Cowlitz Project		(4,114)
Redemption of membership interest related to the New England Black Wolves franchise		(4,499)
Total capital at end of period	(75,692)	137,124	250,707
Retained Earnings (Deficit) | Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period		(41,575)
Total capital at end of period			(41,575)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period	(6,633)	11,062	1,125
Foreign currency translation adjustment	6,904	(17,726)	1,988
Ownership rights settlement related to Project Inspire			271
Redemption of membership interest related to Project Inspire			7,678
Other	(48)	31
Total capital at end of period	223	(6,633)	11,062
Total Capital Attributable to Mohegan Tribal Gaming Authority
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period	130,491	261,769	197,770
Net income (loss)	(162,155)	(2,545)	130,554
Foreign currency translation adjustment	6,904	(17,726)	1,988
Contribution from Mohegan Tribe	10,000
Distributions to Mohegan Tribe	(60,000)	(60,000)	(60,000)
Ownership rights settlement related to Project Inspire			271
Redemption of membership interest related to Project Inspire			(2,318)
Redemption of Mohegan Tribe membership interest related to the Cowlitz Project		(4,114)
Redemption of membership interest related to the New England Black Wolves franchise		(4,499)
Other	(48)	31
Total capital at end of period	(75,469)	130,491	261,769
Total Capital Attributable to Mohegan Tribal Gaming Authority | Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period		(41,575)
Total capital at end of period			(41,575)
Non-controlling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total capital at beginning of period	6,942	9,025	111,399
Net income (loss)	139	169	1,054
Foreign currency translation adjustment	399	(940)	7,374
Ownership rights settlement related to Project Inspire			(6,418)
Redemption of membership interest related to Project Inspire			(104,384)
Redemption of Mohegan Tribe membership interest related to the Cowlitz Project		(5,886)
Redemption of membership interest related to the New England Black Wolves franchise		4,574
Total capital at end of period	7,480	6,942	9,025
Mohegan Tribe
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions from Cowlitz Project		(730)	(6,496)
Mohegan Tribe | Retained Earnings (Deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions from Cowlitz Project		(730)	(6,496)
Mohegan Tribe | Total Capital Attributable to Mohegan Tribal Gaming Authority
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions from Cowlitz Project		(730)	$ (6,496)
Salishan Company, LLC
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions from Cowlitz Project	(661)	(120)
Salishan Company, LLC | Retained Earnings (Deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions from Cowlitz Project	(661)	(120)
Salishan Company, LLC | Total Capital Attributable to Mohegan Tribal Gaming Authority
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions from Cowlitz Project	$ (661)	$ (120)