ORGANIZATION AND BASIS OF PRESENTATION - Schedule of Estimated Fair Value of Financing Facilities and Notes (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Jan. 26, 2021
2021 Senior Unsecured Notes | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note stated interest rate	8.00%	8.00%
2016 7 7/8% Senior Unsecured Notes | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note stated interest rate	7.875%
Carrying Value | Fair Value, Inputs, Level 2 | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	$ 1,942,942
Carrying Value | Fair Value, Inputs, Level 2 | New Senior Secured Credit Facility - Revolving | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	45,000
Carrying Value | Fair Value, Inputs, Level 2 | 2021 Senior Unsecured Notes | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	1,156,911
Carrying Value | Fair Value, Inputs, Level 2 | 2016 7 7/8% Senior Unsecured Notes | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	493,140
Carrying Value | Fair Value, Inputs, Level 2 | MGE Niagara Credit Facility - Revolving | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	28,231
Carrying Value | Fair Value, Inputs, Level 2 | MGE Niagara Credit Facility - Term Loan | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	71,806
Carrying Value | Fair Value, Inputs, Level 3 | MGE Niagara Convertible Debenture | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	32,264
Carrying Value | Fair Value, Inputs, Level 3 | Mohegan Expo Credit Facility | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	26,211
Carrying Value | Fair Value, Inputs, Level 3 | Guaranteed Credit Facility | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	27,789
Carrying Value | Fair Value, Inputs, Level 3 | Redemption Note Payable | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	57,278
Carrying Value | Fair Value, Inputs, Level 3 | Other | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	4,312
Fair Value | Fair Value, Inputs, Level 2 | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	2,032,908
Fair Value | Fair Value, Inputs, Level 2 | New Senior Secured Credit Facility - Revolving | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	44,381
Fair Value | Fair Value, Inputs, Level 2 | 2021 Senior Unsecured Notes | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	1,222,000
Fair Value | Fair Value, Inputs, Level 2 | 2016 7 7/8% Senior Unsecured Notes | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	516,875
Fair Value | Fair Value, Inputs, Level 2 | MGE Niagara Credit Facility - Revolving | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	28,231
Fair Value | Fair Value, Inputs, Level 2 | MGE Niagara Credit Facility - Term Loan | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	72,594
Fair Value | Fair Value, Inputs, Level 3 | MGE Niagara Convertible Debenture | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	32,264
Fair Value | Fair Value, Inputs, Level 3 | Mohegan Expo Credit Facility | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	26,535
Fair Value | Fair Value, Inputs, Level 3 | Guaranteed Credit Facility | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	28,438
Fair Value | Fair Value, Inputs, Level 3 | Redemption Note Payable | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	57,278
Fair Value | Fair Value, Inputs, Level 3 | Other | Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit facility value	$ 4,312