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Commitments (Details) MMcf in Thousands, $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) MMcf MMBbls | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Feb. 14, 2018 USD ($)
Commitments and Contingencies |  |  |  |
Contractual obligation, due in next fiscal year | $ 113,774 |  |  |
Contractual obligation, due in second year | 112,860 |  |  |
Contractual obligation, due in third year | 111,107 |  |  |
Contractual obligation, due in fourth year | 102,606 |  |  |
Contractual obligation, due in fifth year | 72,073 |  |  |
Contractual obligation, due after fifth year | 62,245 |  |  |
Contractual obligation | 574,665 |  |  |
Operating leases, rent expense, net of sublease income | $ 4,800 | $ 5,200 | $ 6,100 |
Crude oil pipeline commitment [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Oil and gas delivery commitments, remaining minimum contractual volumes | MMBbls | 19 |  |  |
Natural gas pipeline commitment [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Oil and gas delivery commitments, remaining minimum contractual volumes | MMcf | 789 |  |  |
Drilling rig leasing contracts [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Contractual obligation | $ 37,800 |  |  |
Early termination penalties for rig contracts | 27,700 |  |  |
Expenses related to early termination of office leases | 0 | $ (8,700) | $ (13,700) |
Pipeline transportation commitments [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Contractual obligation | 463,400 |  |  |
Office space leases [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Contractual obligation | 43,300 |  |  |
Expenses related to early termination of office leases | (3,200) |  |  |
Other miscellaneous contracts and leases [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Contractual obligation | $ 30,200 |  |  |
Electricity purchase agreement [Member] | Subsequent Event [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Contractual obligation |  |  |  | $ 27,900
Water pipeline commitment [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Water delivery commitments, remaining minimum contractual volumes | MMBbls | 24 |  |  |
Outside-operated Eagle Ford divestiture 2017 [Member] | Crude oil pipeline commitment [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Oil, gas, and NGLs delivery commitments, remaining contractual volume on outside-operated Eagle Ford assets | MMBbls | 52 |  |  |
Outside-operated Eagle Ford divestiture 2017 [Member] | Natural gas pipeline commitment [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Oil, gas, and NGLs delivery commitments, remaining contractual volume on outside-operated Eagle Ford assets | MMcf | 514 |  |  |
Outside-operated Eagle Ford divestiture 2017 [Member] | Natural gas liquids pipeline commitment [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Oil, gas, and NGLs delivery commitments, remaining contractual volume on outside-operated Eagle Ford assets | MMBbls | 13 |  |  |
Outside-operated Eagle Ford divestiture 2017 [Member] | Pipeline transportation commitments [Member] |  |  |  |
Commitments and Contingencies |  |  |  |
Contractual obligation, outside-operated Eagle Ford assets | $ 501,900 |  |  |

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