Schedule of Change in Asset Retirement Obligation [Table Text Block] | A reconciliation of the Company’s total asset retirement obligation liability is as follows: | | | | | | | | | | As of December 31, | | 2016 | | 2015 | | (in thousands) | Beginning asset retirement obligation | $ | 140,874 |
| | $ | 122,124 |
| Liabilities incurred (1) | 21,293 |
| | 14,471 |
| Liabilities settled (2) | (57,100 | ) | | (24,781 | ) | Accretion expense | 7,795 |
| | 5,091 |
| Revision to estimated cash flows | 10,445 |
| | 23,969 |
| Ending asset retirement obligation (3)(4) | $ | 123,307 |
| | $ | 140,874 |
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| | (1) | Reflects liabilities incurred through drilling activities and acquisitions of drilled wells. |
| | (2) | Reflects liabilities settled through plugging and abandonment activities and divestitures of properties. |
| | (3) | Balance as of December 31, 2016, included $26.2 million of asset retirement obligations associated with oil and gas properties held for sale, specifically the Company’s outside-operated Eagle Ford shale assets. There were no material asset retirement obligations related to assets held for sale as of December 31, 2015. |
| | (4) | Balances as of December 31, 2016, and 2015, included $932,000 and $3.3 million, respectively, related to the Company’s current asset retirement obligation liability, which is recorded in accounts payable and accrued expenses on the accompanying balance sheets. |
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