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LONG-TERM DEBT (Narrative) (Details) |  |  | 3 Months Ended | 6 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2021 | May 01, 2020 USD ($) | Jun. 30, 2020 USD ($) | Jun. 30, 2019 USD ($) | Jun. 30, 2020 USD ($) | Jun. 30, 2019 USD ($) | Jul. 27, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Nov. 25, 2019 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  | $ 20,802,000 |  | $ 20,802,000 |  |  |  | $ 23,751,000 |
Capitalized interest expense, undeveloped properties |  |  | 500,000 | $ 1,000,000.0 | 700,000 | $ 1,800,000 |  |  |  |
Amount of debt to be repurchased |  |  | 200,000,000 |  | 200,000,000 |  |  |  |  |
Repayments of debt |  |  |  |  | 323,322,000 | 345,350,000 |  |  |  |
Gain on debt extinguishment |  |  | 34,257,000 | $ 0 | 49,579,000 | $ 0 |  |  |  |
Senior notes | Carry value |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Carrying value of notes |  |  | 1,800,000,000 |  | 1,800,000,000 |  |  |  |  |
Senior notes | Fair value | Level 1 |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Carrying value of notes |  |  | 930,200,000 |  | 930,200,000 |  |  |  |  |
Construction loan |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  | 100,000 |  | 100,000 |  |  |  |  |
Revolving Credit Facility |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Amount of principal repurchased |  |  | 47,500,000 |  | 73,300,000 |  |  |  |  |
Repayments of debt |  |  | 12,600,000 |  | 22,800,000 |  |  |  |  |
Gain on debt extinguishment |  |  | 34,300,000 |  | 49,600,000 |  |  |  |  |
6.625% senior unsecured notes due 2023 | Senior notes |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  | $ 324,583,000 |  | $ 324,583,000 |  |  |  | 329,467,000 |
Stated interest rate, percent |  |  | 6.625% |  | 6.625% |  |  |  |  |
Debt issuance costs, net |  |  | $ 2,800,000 |  | $ 2,800,000 |  |  |  |  |
Amount of principal repurchased |  |  | 4,900,000 |  |  |  |  |  |  |
6.000% senior unsecured notes due 2024 | Senior notes |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  | $ 579,568,000 |  | $ 579,568,000 |  |  |  | 603,428,000 |
Stated interest rate, percent |  |  | 6.00% |  | 6.00% |  |  |  |  |
Debt issuance costs, net |  |  | $ 6,100,000 |  | $ 6,100,000 |  |  |  |  |
Amount of principal repurchased |  |  | 16,300,000 |  |  |  |  |  |  |
6.375% senior unsecured notes due 2025 | Senior notes |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  | $ 507,870,000 |  | $ 507,870,000 |  |  |  | 529,525,000 |
Stated interest rate, percent |  |  | 6.375% |  | 6.375% |  |  |  |  |
Debt issuance costs, net |  |  | $ 8,500,000 |  | $ 8,500,000 |  |  |  |  |
Amount of principal repurchased |  |  | 13,500,000 |  |  |  |  |  |  |
6.375% senior unsecured notes due 2026 | Senior notes |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  | $ 374,617,000 |  | $ 374,617,000 |  |  |  | 397,529,000 |
Stated interest rate, percent |  |  | 6.375% |  | 6.375% |  |  |  |  |
Debt issuance costs, net |  |  | $ 3,400,000 |  | $ 3,400,000 |  |  |  |  |
Amount of principal repurchased |  |  | 12,800,000 |  |  |  |  |  |  |
Revolving credit agreement | Revolving credit agreement | Subsequent Event |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  |  |  |  |  |  | $ 750,000,000 |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Credit facility interest rate at the eurodollar rate |  |  |  |  | 2.44% |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Revolving credit agreement |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  |  | 1,500,000,000 |  | $ 1,500,000,000 |  |  |  |  |
Elected commitment amount |  | $ 700,000,000.0 |  |  |  |  |  | $ 1,000,000,000.0 |  | $ 1,200,000,000
Maximum net secured debt to EBITDAX ratio |  | 2.00 |  |  |  |  |  |  |  |
Long-term debt |  |  | 123,000,000 |  | 123,000,000 |  |  |  | $ 120,000,000 |
Remaining borrowing capacity |  |  | 252,900,000 |  | 252,900,000 |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Revolving credit agreement | Forecast |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Net funded debt to EBITDAX ratio | 4.00 |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Letter of credit | Revolving credit agreement |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Credit facility outstanding |  |  | $ 324,100,000 |  | $ 324,100,000 |  |  |  |  |

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