BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair Value of Financial Instruments (Details) - Fair value, inputs, level 2 $ in Thousands	Sep. 30, 2019 USD ($)
Carrying Value | Line of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	$ 1,909,157
Carrying Value | Line of Credit | Revolving Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	102,000
Carrying Value | Line of Credit | Term Loan A Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	263,829
Carrying Value | Line of Credit | Term Loan B Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	805,394
Carrying Value | Line of Credit | MGE Niagara Credit Facility - Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	73,564
Carrying Value | Line of Credit | MGE Niagara Convertible Debenture
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	30,204
Carrying Value | Line of Credit | Mohegan Expo Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	29,357
Carrying Value | Line of Credit | Guaranteed Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	31,840
Carrying Value | Line of Credit | Redemption note payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	81,329
Carrying Value | Line of Credit | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	1,205
Carrying Value | 2016 7 7/8% Senior Unsecured Notes | 2016 7 7/8% Senior Unsecured Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Note value	$ 490,435
Note stated interest rate	7.875%
Estimate of Fair Value Measurement | Line of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	$ 1,845,472
Estimate of Fair Value Measurement | Line of Credit | Revolving Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	96,645
Estimate of Fair Value Measurement | Line of Credit | Term Loan A Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	257,342
Estimate of Fair Value Measurement | Line of Credit | Term Loan B Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	759,618
Estimate of Fair Value Measurement | Line of Credit | MGE Niagara Credit Facility - Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	74,566
Estimate of Fair Value Measurement | Line of Credit | MGE Niagara Convertible Debenture
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	30,204
Estimate of Fair Value Measurement | Line of Credit | Mohegan Expo Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	30,282
Estimate of Fair Value Measurement | Line of Credit | Guaranteed Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	33,031
Estimate of Fair Value Measurement | Line of Credit | Redemption note payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	81,329
Estimate of Fair Value Measurement | Line of Credit | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facility value	1,205
Estimate of Fair Value Measurement | 2016 7 7/8% Senior Unsecured Notes | 2016 7 7/8% Senior Unsecured Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Note value	$ 481,250