Organization and Basis of Presentation - Estimated Fair Values of Long-term Debt (Details) - Fair Value, Inputs, Level 2 $ in Thousands	Jun. 30, 2020 USD ($)
Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,040,840
Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,751,745
Revolving Credit Facility | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	247,000
Revolving Credit Facility | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	202,540
Term Loan A Facility | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	237,664
Term Loan A Facility | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	201,812
Term Loan B Facility | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	801,752
Term Loan B Facility | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	665,904
2016 7 7/8% Senior Unsecured Notes | Carrying Value | Senior Unsecured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	491,618
2016 7 7/8% Senior Unsecured Notes | Fair Value | Senior Unsecured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note value	416,250
MGE Niagara Credit Facility - Revolving | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	25,655
MGE Niagara Credit Facility - Revolving | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	25,655
MGE Niagara Credit Facility - Term Loan | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	68,822
MGE Niagara Credit Facility - Term Loan | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	69,635
MGE Niagara Convertible Debentures | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	29,320
MGE Niagara Convertible Debentures | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	29,320
Mohegan Expo Credit Facility | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	28,368
Mohegan Expo Credit Facility | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	29,033
Guaranteed Credit Facility | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	30,108
Guaranteed Credit Facility | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	31,063
Redemption Note Payable | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	76,629
Redemption Note Payable | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	76,629
Other | Carrying Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,904
Other | Fair Value | Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 3,904