LONG-TERM DEBT - Schedules and Introduction (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Oct. 31, 2016
Debt Schedule [Abstract]
Long-term debt	$ 1,909,157	$ 1,814,155
Less: current portion of long-term debt	(76,909)	(73,232)
Long-term debt, net of current portion	1,832,248	1,740,923
Credit Facility | Senior Secured Credit Facility - Revolving
Debt Schedule [Abstract]
Long-term debt	102,000	66,000
Debt issuance costs	1,191	1,262
Credit Facility | Senior Secured Credit Facility - Term Loan A, due June 2018
Debt Schedule [Abstract]
Long-term debt	263,829	311,466
Debt issuance costs	4,236	6,661
Credit Facility | Senior Secured Credit Facility - Term Loan B, due June 2018
Debt Schedule [Abstract]
Long-term debt	805,394	810,430
Debt issuance costs	16,925	20,571
Credit Facility | 2016 7 7/8% Senior Unsecured Notes, net of discount and debt issuance costs of $11,033 and $12,383, respectively
Debt Schedule [Abstract]
Long-term debt	490,435	488,967
Credit Facility | MGE Niagara Credit Facility - Term Loan
Debt Schedule [Abstract]
Long-term debt	73,564	0
Debt issuance costs	1,002
Credit Facility | Mohegan Expo Credit Facility, net of debt issuance costs of $1,319 and $1,683, respectively
Debt Schedule [Abstract]
Long-term debt	29,357	31,980
Debt issuance costs	925	1,319
Credit Facility | Guaranteed Credit Facility, net of debt issuance costs of $1,262
Debt Schedule [Abstract]
Long-term debt	31,840	22,403
Convertible Debenture | MGE Niagara Convertible Debenture
Debt Schedule [Abstract]
Long-term debt	30,204	0
Notes payable to banks | Redemption note payable
Debt Schedule [Abstract]
Long-term debt	81,329	81,165
Debt issuance costs	$ 23,905	33,635
2016 7 7/8% Senior Unsecured Notes | 2016 7 7/8% Senior Unsecured Notes, net of discount and debt issuance costs of $11,033 and $12,383, respectively
Debt Schedule [Abstract]
Note stated interest rate	7.875%		7.875%
Debt issuance costs	$ 9,565	11,033
2016 7 7/8% Senior Unsecured Notes | Other
Debt Schedule [Abstract]
Long-term debt	$ 1,205	$ 1,744