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Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement gain or loss | $ (70,305) | $ (24,722) | $ (286,270) | $ (23,843)
Net derivative (gain) loss | 63,871 | (100,889) | (314,269) | (3,463)
Oil Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement gain or loss | (68,907) | 2,246 | (261,095) | 14,304
Net derivative (gain) loss | 30,641 | (83,984) | (360,649) | 67,261
Gas Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement gain or loss | (896) | (12,210) | (16,575) | (13,744)
Net derivative (gain) loss | 31,548 | (4,228) | 46,537 | (36,337)
NGL Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement gain or loss | (502) | (14,758) | (8,600) | (24,403)
Net derivative (gain) loss | $ 1,682 | $ (12,677) | $ (157) | $ (34,387)

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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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