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Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
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Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | $ 158,822 | $ (142,528) | $ 266,707 | $ (215,965)
Net derivative (gain) loss | 370,348 | 167,200 | 715,037 | (378,140)
Oil Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | 134,298 | (138,606) | 190,627 | (192,188)
Net derivative (gain) loss | 277,215 | 151,250 | 543,030 | (391,290)
Gas Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | 12,232 | (1,054) | 52,680 | (15,679)
Net derivative (gain) loss | 61,364 | 8,261 | 110,286 | 14,989
NGL Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | 12,292 | (2,868) | 23,400 | (8,098)
Net derivative (gain) loss | $ 31,769 | $ 7,689 | $ 61,721 | $ (1,839)

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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=125515794&loc=SL5618551-113959 + Details
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