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Derivative Instruments - Gain (Loss) on Derivative Instruments (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Derivative [Line Items] |  |  |
Net gain (loss) on natural gas, oil, and NGL derivatives | $ 65,291 | $ 208,360 | $ (123,479)
Natural gas derivatives |  |  |
Derivative [Line Items] |  |  |
Net gain (loss) on natural gas, oil, and NGL derivatives | 23,765 | 194,450 | (116,130)
Oil derivatives |  |  |
Derivative [Line Items] |  |  |
Net gain (loss) on natural gas, oil, and NGL derivatives | 43,510 | 7,035 | (13,084)
NGL derivatives |  |  |
Derivative [Line Items] |  |  |
Net gain (loss) on natural gas, oil, and NGL derivatives | (603) | 6,632 | 5,735
Contingent consideration arrangement |  |  |
Derivative [Line Items] |  |  |
Net gain (loss) on natural gas, oil, and NGL derivatives | $ (1,381) | $ 243 | $ 0

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- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details
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