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Derivative Financial Instruments Gains and Losses (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Derivative, (Gain) Loss on Derivative, Net [Abstract] |  |  |  |
Derivative Settlement (Gain) Loss |  | $ (329,478) | $ (512,566) | $ (12,615)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net |  | 250,633 | (408,831) | (583,264)
NYMEX Oil Contracts [Member] |  |  |  |
Derivative, (Gain) Loss on Derivative, Net [Abstract] |  |  |  |
Derivative Settlement (Gain) Loss |  | (243,102) | (362,219) | (28,410)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net |  | 85,370 | (191,165) | (457,082)
Gas Contracts [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain on Early Settlement of Derivatives |  |  | 15,300 | 5,600
Derivative, (Gain) Loss on Derivative, Net [Abstract] |  |  |  |
Derivative Settlement (Gain) Loss | [1] | (94,936) | (123,180) | 26,706
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net |  | 81,060 | (189,734) | (93,267)
NGL Contracts [Member] |  |  |  |
Derivative, (Gain) Loss on Derivative, Net [Abstract] |  |  |  |
Derivative Settlement (Gain) Loss |  | 8,560 | (27,167) | (10,911)
Derivative Instruments Not Designated as Hedging Instruments, (Gain) Loss, Net |  | $ 84,203 | $ (27,932) | $ (32,915)
Cash Flow Hedging [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Number of Instruments Held |  | 0 | 0 | 0
[1] | Natural gas derivative settlements for the years ended December 31, 2015, and 2014, include $15.3 million and $5.6 million, respectively, of early settlements of futures contracts as a result of divesting assets in the Company’s Mid-Continent region.

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