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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, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | $ 40,718 | $ (13,092) | $ 101,911 | $ (29,402)
Net derivative (gain) loss | 178,026 | 80,599 | 249,304 | (89,364)
Oil Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | 16,798 | 2,472 | 61,976 | 14,310
Net derivative (gain) loss | 110,413 | 45,874 | 146,781 | (41,910)
Gas Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | 802 | (24,088) | (4,851) | (63,345)
Net derivative (gain) loss | 4,309 | (6,068) | 21,299 | (56,574)
NGL Contracts [Member] |  |  |  |
Derivative Instruments, (Gain) Loss [Line Items] |  |  |  |
Derivative settlement (gain) loss | 23,118 | 8,524 | 44,786 | 19,633
Net derivative (gain) loss | $ 63,304 | $ 40,793 | $ 81,224 | $ 9,120

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- Definition Realized gain or loss recognized in earnings from the settlement of derivative instruments not designated as hedges. + References No definition available. + Details
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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=109980867&loc=SL5618551-113959 + Details
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