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LONG-TERM DEBT (Narrative) (Details) - USD ($) shares in Millions |  |  | 3 Months Ended | 4 Months Ended | 5 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Oct. 14, 2021 | May 17, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | May 17, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | May 16, 2021 | Dec. 31, 2020
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debtor-in-possession financing, letters of credit outstanding |  |  |  | $ 262,500,000 |  | $ 262,500,000 |  |  |
Debtor-in-possession financing, amount arranged |  |  |  | 105,000,000 |  | 105,000,000 |  |  |
Debtor-in-possession financing, borrowings outstanding |  |  |  | 157,500,000 |  | 157,500,000 |  |  |
Interest capitalized |  |  |  | 117,000 | $ 0 |  | $ 907,000 |  |
Oil and Gas Properties |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Interest capitalized |  |  | $ 200,000 | 100,000 | 0 |  | $ 900,000 |  |
Senior Notes |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Consideration received on transaction |  |  |  | 550,000,000 |  |  |  |  |
Number of shares issued in transaction (in shares) |  | 19.7 |  |  |  |  |  |  |
Senior Notes | Carry Value |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Carrying value of notes |  |  |  | 548,900,000 |  | 548,900,000 |  |  |
Senior Notes | Fair Value | Level 1 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Carrying value of notes |  |  |  | 601,400,000 |  | 601,400,000 |  |  |
Exit Facility |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Line of credit facility, commitment fee amount |  | $ 150,000,000 |  |  |  |  |  |  |
Remaining borrowing capacity |  | 40,000,000 |  |  | 40,000,000 |  |  |  |
Long-term debt |  |  |  | 35,606,000 |  | $ 35,606,000 |  |  | $ 0
Exit Facility | Revolving Credit Agreement |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Weight average interest rate |  |  |  |  |  | 4.50% |  |  |
First-Out Term Loan |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  | $ 165,000,000 |  | $ 165,000,000 |  |  | 0
First-Out Term Loan | Revolving Credit Agreement |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Weight average interest rate |  |  |  |  |  | 5.50% |  |  |
8.000% senior unsecured notes due 2026 |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  | 8.00% |  | 8.00% |  |  |
Long-term debt |  |  |  | $ 550,000,000 |  | $ 550,000,000 |  |  | $ 0
8.000% senior unsecured notes due 2026 | Senior Notes |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debtor-in-possession financing, amount arranged |  | 550,000,000 |  |  | 550,000,000 |  |  |  |
8.000% senior unsecured notes due 2026 | Senior Notes | Fresh Start Adjustments |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt instrument, amount |  | $ 550,000,000 |  |  | $ 550,000,000 |  |  |  |
Stated interest rate |  | 8.00% |  |  | 8.00% |  |  |  |
6.625% senior unsecured notes due 2023 | Senior Notes |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  |  |  |  |  |  | 6.625%
Long-term debt |  |  |  | 0 |  | 0 |  |  | $ 324,583,000
6.000% senior unsecured notes due 2024 | Senior Notes |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  |  |  |  |  |  | 6.00%
Long-term debt |  |  |  | 0 |  | 0 |  |  | $ 579,568,000
6.375% senior unsecured notes due 2025 | Senior Notes |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  |  |  |  |  |  | 6.375%
Long-term debt |  |  |  | 0 |  | 0 |  |  | $ 507,870,000
6.375% senior unsecured notes due 2026 | Senior Notes |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  |  |  |  |  |  | 6.375%
Long-term debt |  |  |  | 0 |  | 0 |  |  | $ 374,617,000
Revolving Credit Facility |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debtor-in-possession financing, amount arranged |  | $ 580,000,000 |  |  | $ 580,000,000 |  |  |  |
Revolving Credit Facility | New Credit Facility | Subsequent Event |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Aggregate maximum principal amount | $ 1,500,000,000 |  |  |  |  |  |  |  |
Initial borrowing base amount | 850,000,000 |  |  |  |  |  |  |  |
Line of credit facility, commitment fee amount | 700,000,000 |  |  |  |  |  |  |  |
Revolving Credit Facility | Exit Facility |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debtor-in-possession financing, amount arranged |  | 1,500,000,000 |  |  | 1,500,000,000 |  |  |  |
Revolving Credit Facility | Exit Facility | Fresh Start Adjustments |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt instrument, amount |  | 1,500,000,000 |  |  | 1,500,000,000 |  |  |  |
Line of credit facility, commitment fee amount |  | 580,000,000 |  |  |  |  |  |  |
Revolving Credit Facility | First-Out Term Loan |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility outstanding |  | 15,000,000 |  |  | 15,000,000 |  |  |  |
Debtor-in-possession financing, amount arranged |  | 180,000,000 |  |  | 180,000,000 |  |  |  |
Revolving Credit Facility | First-Out Term Loan | Fresh Start Adjustments |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt instrument, amount |  | $ 180,000,000 |  |  | $ 180,000,000 |  |  |  |
Revolving Credit Facility | Pre-Petition Revolving Credit Facility |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Initial borrowing base amount |  |  |  |  |  |  |  | $ 580,000,000 |
Revolving Credit Agreement | Pre-Petition Revolving Credit Facility |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  | 0 |  | 0 |  |  | 292,910,000
Revolving Credit Agreement | DIP Credit Facility |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  | 0 |  | 0 |  |  | $ 157,500,000
Letter of Credit |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  | $ 115,500,000 |  | $ 115,500,000 |  |  |
Letter of Credit | New Credit Facility | Subsequent Event |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Aggregate maximum principal amount | $ 175,000,000 |  |  |  |  |  |  |  |

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