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LONG-TERM DEBT (Narrative) (Details) - USD ($) shares in Millions |  | 1 Months Ended | 3 Months Ended | 5 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
May 17, 2021 | Jun. 30, 2021 | Jun. 30, 2020 | May 17, 2021 | Jun. 30, 2021 | Jun. 30, 2020 | Dec. 31, 2020 | Oct. 08, 2020
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument current ratio | 100.00% |  |  |  |  |  |  |
Unused capacity, commitment fee percentage | 0.50% |  |  |  |  |  |  |
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 |  | 0 |  | $ 0 |  | $ 710,000 |  |
Oil and Gas Properties |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest capitalized |  | 0 | $ 500,000 | 0 |  | $ 700,000 |  |
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 |  | 548,800,000 |  |  | 548,800,000 |  |  |
Senior Notes | Fair Value | Level 1 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Carrying value of notes |  | 592,600,000 |  |  | 592,600,000 |  |  |
Exit Facility |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of credit facility, commitment fee amount | $ 150,000,000.0 |  |  |  |  |  |  |
Debt instrument net funded leverage ratio | 300.00% |  |  |  |  |  |  |
Debt instrument net senior secured leverage ratio | 200.00% |  |  |  |  |  |  |
Remaining borrowing capacity | $ 40,000,000 |  |  | $ 40,000,000 |  |  |  |
Long-term debt |  | 105,000,000 |  |  | 105,000,000 |  | $ 0 |
Exit Facility | Loan Parties |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Stated interest rate | 85.00% |  |  | 85.00% |  |  |  |
Exit Facility | LIBOR | Minimum |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 3.00% |  |  |  |  |  |  |
Exit Facility | LIBOR | Maximum |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 4.00% |  |  |  |  |  |  |
Exit Facility | Base Rate | Minimum |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 2.00% |  |  |  |  |  |  |
Exit Facility | Base Rate | Maximum |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 3.00% |  |  |  |  |  |  |
First-Out Term Loan |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long-term debt |  | $ 180,000,000 |  |  | $ 180,000,000 |  | 0 |
First-Out Term Loan | LIBOR |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 4.50% |  |  |  |  |  |  |
First-Out Term Loan | LIBOR | Interest Rate |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 1.00% |  |  |  |  |  |  |
First-Out Term Loan | Base Rate |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 3.50% |  |  |  |  |  |  |
First-Out Term Loan | Base Rate | Interest Rate |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Variable interest rate | 2.00% |  |  |  |  |  |  |
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 | Fresh Start Adjustments |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument interest computation basis |  | 360-day year of twelve 30-day months |  |  |  |  |  |
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% |  |  | 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% |  |  | 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% |  |  | 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% |  |  | 6.375% |  |  |  |
Long-term debt |  | 0 |  |  | $ 0 |  | 374,617,000 |
DIP Credit Facility | Revolving Credit Agreement |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Weight average interest rate |  |  |  |  | 4.50% | 5.50% |  |
Revolving Credit Facility |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debtor-in-possession financing, amount arranged | $ 580,000,000 |  |  | $ 580,000,000 |  |  |  |
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 | 580,000,000.0 |  |  |  |  |  |  |
Revolving Credit Facility | First-Out Term Loan |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility outstanding | 15,000,000.0 |  |  | 15,000,000.0 |  |  |  |
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 | $ 180,000,000.0 |  |  | $ 180,000,000.0 |  |  |  |
Revolving Credit Facility | Pre-petition revolving credit facility |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Elected commitment 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 |  | $ 114,800,000 |  |  | $ 114,800,000 |  |  |

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