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Acquisitions (Details) |  |  |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 12 Months Ended | 21 Months Ended |
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Aug. 31, 2015 USD ($) | Jun. 29, 2015 USD ($) a | Jun. 12, 2015 USD ($) a well mi MMcf | Jun. 09, 2015 USD ($) a | Apr. 21, 2015 USD ($) | Mar. 20, 2014 USD ($) | Nov. 13, 2013 USD ($) | Feb. 15, 2013 USD ($) | Apr. 30, 2015 USD ($) a | Feb. 28, 2011 | Dec. 31, 2015 USD ($) | 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 ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2015 USD ($) | Feb. 28, 2014 a
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of common stock, net of offering costs and exercise of stock options |  |  | $ 479,700,000 |  | $ 501,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 981,568,000 | $ 689,000 | $ 766,495,000 |  |
Revenues |  |  |  |  |  |  |  |  |  |  | $ 190,319,000 | $ 230,569,000 | $ 112,270,000 | $ 176,317,000 | $ 267,697,000 | $ 170,804,000 | $ 114,736,000 | $ 118,029,000 | 709,475,000 | 671,266,000 | 262,753,000 |  |
Lease operating expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 69,475,000 | 52,191,000 | 26,703,000 |  |
Period allowed for refusal |  |  |  |  |  |  |  |  |  | 6 months |  |  |  |  |  |  |  |  |  |  |  |  |
Affiliates participation ratio |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Gas And Oil Area, Gross | a |  | 4,950 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deductions to cash held in escrow |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,000 | $ 8,000 | $ 8,000 |  |
Common Stock | Public Offering |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of common stock, net of offering costs and exercise of stock options |  |  |  |  |  |  | $ 408,000,000 | $ 325,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Utica Shale |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas and oil acreage, undeveloped, net | a |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,000
Purchase price |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 182,000,000 |  |  |  |
Cash, net of purchase price adjustments |  |  |  |  |  | $ 179,527,000 |  |  |  |  |  |  |  |  |  |  |  |  | 179,500,000 |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6,400,000 |
Lease operating expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,000,000 |
Goodwill, Acquired During Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |
Paloma Partners III, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount put in escrow | $ 30,100,000 |  |  |  |  |  |  |  | $ 75,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase price | $ 302,300,000 |  |  |  |  |  |  |  | $ 301,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas And Oil Area, Net | a |  |  |  |  |  |  |  |  | 24,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
American Energy - Utica, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount put in escrow |  |  |  | $ 67,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase price |  | $ 405,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash, net of purchase price adjustments |  | 405,000,000 | $ 405,029,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deductions to cash held in escrow |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,400,000 |  |  |  |
Goodwill, Acquired During Period |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Belmont And Jefferson Counties, Ohio |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas And Oil Area, Gross And Net | a |  |  |  | 6,198 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase price |  |  |  | $ 68,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Monroe County, Ohio |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas And Oil Area, Net | a |  |  | 27,228 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas And Oil Area, Gross | a |  |  | 38,965 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Monroe County, Ohio | American Energy - Utica, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase price |  | $ 18,200,000 | $ 319,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas And Oil Area, Net | a |  | 1,900 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Oil And Gas Delivery Commitments And Contracts, Daily Production, Volume | MMcf |  |  | 14.6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Productive Oil And Gas Wells, Number Of Wells, Gross | well |  |  | 18 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Productive Oil And Gas Wells, Number Of Wells, Net | well |  |  | 11.3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas Gathering, Transportation, Length | mi |  |  | 11 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Locations For Productive Wells | well |  |  | 4 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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