Asset Retirement Obligations - Reconciliation of Asset Retirement Obligations Liability (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] | |||
| Asset retirement obligations, beginning of period | $ 334,438 | $ 378,322 | |
| Asset retirement obligation settlements | (72,409) | (72,320) | $ (32,555) |
| Accretion of discount | 17,172 | 17,571 | 20,703 |
| Liabilities incurred | 163 | 398 | |
| Revisions of estimated liabilities | 21,082 | 10,467 | |
| Asset retirement obligations, end of period | 300,446 | 334,438 | $ 378,322 |
| Less current portion | 23,613 | 78,264 | |
| Long-term | $ 276,833 | $ 256,174 | |
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of cash paid during the period to settle an asset retirement obligation. Amounts paid to settle an asset retirement obligation are generally included in the operating section of the Statement of Cash Flows. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of asset retirement obligations incurred during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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- Definition Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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