CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Cash flows provided by (used in) operating activities:
Net loss	$ (140,031)	$ (12,284)	$ (130,607)	$ (1,576)
Adjustments to reconcile net loss to net cash flows provided by (used in) operating activities:
Depreciation and amortization	27,826	42,782	56,370	69,872
Non-cash operating lease expense			6,403	0
Accretion of discounts			584	523
Amortization of discounts and debt issuance costs			9,256	9,663
Provision for losses on receivables			1,977	490
Impairment of Mohegan Sun Pocono's intangible assets	126,596		126,596	0
Deferred income tax provision			(484)	0
Other, net			1,063	(357)
Changes in operating assets and liabilities, net of effect of the MGE Niagara Resorts acquisition:
Accounts receivable			13,057	304
Accrued interest on notes receivable related to the Cowlitz Project				72,001
Inventories			1,297	585
Due from Ontario Lottery and Gaming Corporation			1,910	0
Casino Operating and Services Agreement customer contract asset			(76,290)	0
Other assets			8,847	(4,921)
Trade payables			10,755	1,663
Accrued interest			(55)	170
Due to Ontario Lottery and Gaming Corporation			1,868	0
Operating lease liabilities			(3,861)	0
Other liabilities			(45,549)	(4,309)
Net cash flows provided by (used in) operating activities			(16,863)	144,108
Cash flows used in investing activities:
Purchases of property and equipment			(54,630)	(36,364)
Acquisition of the MGE Niagara Resorts, net of cash acquired			(1,666)	0
Proceeds from notes receivable related to the Cowlitz Project				32,026
Investment in Mohegan Hotel Holding, LLC			(10,750)	0	$ (5,000)
Other, net			(1,172)	(1,205)
Net cash flows used in investing activities			(68,218)	(5,543)
Cash flows provided by (used in) financing activities:
Other borrowings				11,335
Other repayments			(11,617)	(2,784)
Payments on finance lease obligations			(828)	0
Distributions			(24,000)	(24,000)
Redemption of Mohegan Tribe membership interest in the Cowlitz Project				(10,000)
Other, net			(1,527)	(1,776)
Net cash flows provided by (used in) financing activities			104,604	(76,670)
Net increase in cash, cash equivalents, restricted cash and restricted cash equivalents			19,523	61,895
Effect of exchange rate on cash, cash equivalents, restricted cash and restricted cash equivalents			(3,567)	(3,706)
Cash, cash equivalents, restricted cash and restricted cash equivalents at beginning of period			280,729	234,626	234,626
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	296,685	292,815	296,685	292,815	280,729
Reconciliation of cash, cash equivalents, restricted cash and restricted cash equivalents to the condensed consolidated balance sheets:
Cash and cash equivalents	184,868	91,396	184,868	91,396	130,138
Restricted cash and cash equivalents	1,707	1,314	1,707	1,314	4,960
Restricted cash and cash equivalents	110,110	200,105	110,110	200,105	145,631
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	$ 296,685	$ 292,815	296,685	292,815	$ 280,729
Supplemental disclosures:
Cash paid for interest			61,583	61,310
Non-cash transactions:
Right-of-use operating lease assets			360,257	0
Right-of-use operating lease obligations			360,402	0
Finance lease assets and obligations			2,206	0
Construction payables			45,395	12,808
Payment by third-party for interactive gaming license				8,000
MGE Niagara Resorts - derecognition of build-to-suit asset and liability			90,675	0
Credit Facility | Bank of America, N.A. Revolving and Line of Credit
Cash flows provided by (used in) financing activities:
Senior secured credit facility borrowings - revolving and line of credit			665,725	641,230
Senior secured credit facility repayments			(520,725)	(652,230)
Credit Facility | MGE Niagara Resorts Credit Facility - Revolving
Cash flows provided by (used in) financing activities:
Senior secured credit facility borrowings - revolving and line of credit			77,537	0
Senior secured credit facility repayments			(51,110)	0
Credit Facility | Senior Secured Credit Facility, Term Loan A and Term Loan B
Non-cash transactions:
Senior secured credit facility reductions			10,514	13,295
Convertible Debenture | Senior Secured Credit Facility, Term Loan A and Term Loan B
Cash flows provided by (used in) financing activities:
Senior secured credit facility repayments			(26,590)	(37,715)
Convertible Debenture | MGE Niagara Credit Facility
Cash flows provided by (used in) financing activities:
Senior secured credit facility repayments			(1,848)	0
Salishan Company, LLC
Cash flows provided by (used in) financing activities:
Distributions			$ (413)	$ (730)