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Fair Value Measurements (Tables) | 12 Months Ended
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Dec. 31, 2020
Fair Value Disclosures [Abstract] |
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] | The following table is a listing of the Company’s assets and liabilities that are measured at fair value in the accompanying balance sheets and where they are classified within the fair value hierarchy as of December 31, 2020:
| Level 1 |  | Level 2 |  | Level 3
| (in thousands)
Assets: |  |  |  |  |
Derivatives (1) | $ | — |  |  | $ | 54,353 |  |  | $ | — |
Liabilities: |  |  |  |  |
Derivatives (1) | $ | — |  |  | $ | 222,520 |  |  | $ | — |
____________________________________________ (1) This represents a financial asset or liability that is measured at fair value on a recurring basis. The following table is a listing of the Company’s assets and liabilities that are measured at fair value in the accompanying balance sheets and where they are classified within the fair value hierarchy as of December 31, 2019:
| Level 1 |  | Level 2 |  | Level 3
| (in thousands)
Assets: |  |  |  |  |
Derivatives (1) | $ | — |  |  | $ | 75,808 |  |  | $ | — |
Liabilities: |  |  |  |  |
Derivatives (1) | $ | — |  |  | $ | 54,290 |  |  | $ | — |
____________________________________________ (1) This represents a financial asset or liability that is measured at fair value on a recurring basis.
Impairment of Oil and Gas Properties [Table Text Block] | The following table presents impairment of proved properties expense and abandonment and impairment of unproved properties expense recorded for the periods presented:
| For the Years Ended December 31,
| 2020 |  | 2019 |  | 2018
| (in millions)
Impairment of proved oil and gas properties and related support equipment | $ | 956.7 |  |  | $ | — |  |  | $ | — |
Abandonment and impairment of unproved properties (1) | 59.3 |  |  | 33.8 |  |  | 49.9 |
Impairment | $ | 1,016.0 |  |  | $ | 33.8 |  |  | $ | 49.9 |
____________________________________________ (1) These impairments related to actual and anticipated lease expirations, as well as actual and anticipated losses on acreage due to title defects, changes in development plans, and other inherent acreage risks. The balances in the unproved oil and gas properties line item on the accompanying balance sheets as of December 31, 2020, 2019, and 2018, are recorded at carrying value. Please refer to Note 1 – Summary of Significant Accounting Policies for information on the Company’s policies for determining fair value of its oil and gas producing properties and related impairment expense.
Long Term Debt Fair Value [Table Text Block] | The following table reflects the fair value of the Company’s senior note obligations measured using Level 1 inputs based on quoted secondary market trading prices. These notes were not presented at fair value on the accompanying balance sheets as of December 31, 2020, or 2019, as they were recorded at carrying value, net of any unamortized discounts and deferred financing costs. Please refer to Note 5 – Long-Term Debt for additional information.
| As of December 31,
| 2020 |  | 2019
| Principal Amount |  | Fair Value |  | Principal Amount |  | Fair Value
| (in thousands)
1.50% Senior Secured Convertible Notes due 2021 (1) | $ | 65,485 |  |  | $ | 61,449 |  |  | $ | — |  |  | $ | — |
10.0% Senior Secured Notes due 2025 | $ | 446,675 |  |  | $ | 482,887 |  |  | $ | — |  |  | $ | — |
6.125% Senior Unsecured Notes due 2022 | $ | 212,403 |  |  | $ | 205,379 |  |  | $ | 476,796 |  |  | $ | 481,564 |
5.0% Senior Unsecured Notes due 2024 | $ | 277,034 |  |  | $ | 240,072 |  |  | $ | 500,000 |  |  | $ | 479,815 |
5.625% Senior Unsecured Notes due 2025 | $ | 349,118 |  |  | $ | 289,401 |  |  | $ | 500,000 |  |  | $ | 475,835 |
6.75% Senior Unsecured Notes due 2026 | $ | 419,235 |  |  | $ | 342,385 |  |  | $ | 500,000 |  |  | $ | 494,860 |
6.625% Senior Unsecured Notes due 2027 | $ | 416,791 |  |  | $ | 331,220 |  |  | $ | 500,000 |  |  | $ | 493,750 |
1.50% Senior Convertible Notes due 2021 (1) | $ | — |  |  | $ | — |  |  | $ | 172,500 |  |  | $ | 164,430 |
___________________________________________ (1) The Company’s 2021 Senior Convertible Notes became secured in the second quarter of 2020 upon the closing of the Exchange Offers. Please refer to Note 5 – Long-Term Debt for additional information.

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- Definition Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19279-110258 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2C -URI http://asc.fasb.org/extlink&oid=117815213&loc=SL7498348-110258 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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