| **Assets Held for Sale, Divestitures and Discontinued Operations (Tables)** | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
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| **Discontinued Operations and Disposal Groups [Abstract]**                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Schedule of Discontinued Operations                                         | The tables below set forth selected financial information related to net assets held for sale and operating results related to discontinued operations. Net assets held for sale represents the Appalachian Basin assets that are expected to be sold, net of liabilities that are expected to be assumed by the purchaser.The following table presents balance sheet data related to our pro rata share of these assets held for sale as of September 30, 2013:Balance Sheet Net Assets Held for Sale  (in thousands)Assets  Properties and equipment $130,835Accumulated depreciation, depletion and amortization (101,801)Total Assets 29,034   Liabilities  Asset retirement obligation 22,788   Net Assets $6,246       The following table presents statement of operations data related to our discontinued operations for the Piceance Basin, NECO and Permian Basin divestiture:  Three Months Ended September 30, Nine Months Ended September 30,Statements of Operations - Discontinued Operations 2013 2012 2013 2012  (in thousands)Revenues        Crude oil, natural gas and NGLs sales $(58) $7,624 $20,398 $25,972Sales from natural gas marketing 1,789 392 2,825 1,149Well operations, pipeline income and other 31 446 890 1,476Total revenues 1,762 8,462 24,113 28,597         Costs, expenses and other        Production costs 18 4,959 7,975 17,743Cost of natural gas marketing 1,679 338 2,673 1,010Depreciation, depletion and amortization — 10,362 2,258 32,873Other 77 298 2,531 949(Gain) loss on sale of properties and equipment 1,254 — 2,330 (19,920)Total costs, expenses and other 3,028 15,957 17,767 32,655         Income (loss) from discontinued operations (1,266) (7,495)6,346 (4,058)Provision for income taxes 484 2,863 (2,175) 1,590Income (loss) from discontinued operations, net of tax $(782) $(4,632)$4,171 $(2,468)          While the reclassification of revenues and expenses related to discontinued operations for the prior period had no impact upon previously reported net earnings, the statement of operations table presents the revenues and expenses that were reclassified from the specified statement of operations line items to discontinued operations. |

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| - Definition
Tabular disclosure of disposal groups, which may include the gain (loss) recognized in the income statement and the income statement caption that includes that gain (loss), amounts of revenues and pretax profit or loss reported in discontinued operations, the classification and carrying value of the assets and liabilities comprising the disposal group, and the segment in which the disposal group was reported. Also may include the amount of adjustments to amounts previously reported in discontinued operations such as resolution of contingencies arising from the disposal transaction or the operations of the component prior to disposal.
+ References
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