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DERIVATIVE INSTRUMENTS (Net (Loss) Gain on Derivative Instruments) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Derivative [Line Items] |  |  |  |
Net gain (loss) on natural gas, oil and NGLs derivatives | $ 27,074 | $ (9,663) | $ 178,169 | $ (96,737)
Natural gas derivatives |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain (loss) on natural gas, oil and NGLs derivatives | 11,731 | 14,101 | 147,774 | (26,789)
Oil derivatives |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain (loss) on natural gas, oil and NGLs derivatives | 12,736 | (11,610) | 24,153 | (45,176)
NGLs derivatives |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain (loss) on natural gas, oil and NGLs derivatives | 3,641 | (12,154) | 7,276 | (24,772)
Contingent consideration arrangement |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain (loss) on natural gas, oil and NGLs derivatives | $ (1,034) | $ 0 | $ (1,034) | $ 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=109980867&loc=SL5618551-113959 + Details
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