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Acquisitions and Divestitures - Acquisitions (Details) a in Thousands, $ in Thousands |  |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Jul. 01, 2015 USD ($) | Oct. 01, 2013 USD ($) a seller | Sep. 26, 2013 USD ($) a | Dec. 31, 2015 USD ($) | Sep. 30, 2015 USD ($) | Jun. 30, 2015 USD ($) | Mar. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Sep. 30, 2014 USD ($) | Jun. 30, 2014 USD ($) | Mar. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  | $ 182,067 | $ 197,235 | $ 230,046 | $ 180,387 | $ 299,672 | $ 368,659 | $ 372,378 | $ 349,519 |  | $ 789,735 | $ 1,390,228 | $ 1,141,999
Operating income (loss) |  |  |  | $ (53,166) | $ (19,926) | $ (7,437) | $ (33,635) | $ 15,924 | $ 134,103 | $ 166,545 | $ 329,080 |  | $ (114,164) | $ 645,652 | $ 504,398
West Williston |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of sellers | seller |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |
Acres acquired | a |  | 136 |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred |  | $ 1,475,361 |  |  |  |  |  |  |  |  |  |  |  |  |
Recognized identifiable assets acquired |  | $ 1,475,361 |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  | $ 57,600 |  |  |
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  | 14,900 |  |  |
Acquisition costs |  |  |  |  |  |  |  |  |  |  |  | $ 2,000 |  |  |
East Nesson |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Acres acquired | a |  |  | 25 |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred |  |  | $ 56,750 |  |  |  |  |  |  |  |  |  |  |  |
Recognized identifiable assets acquired |  |  | 56,750 |  |  |  |  |  |  |  |  |  |  |  |
Capital spending commitment |  |  | $ 8,200 |  |  |  |  |  |  |  |  |  |  |  |
Payment to seller for remaining committed amount for drilling and completion activities | $ 3,200 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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