| **Properties and Equipment (Tables)**            | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
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| **Property, Plant and Equipment [Abstract]**     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Property, Plant and Equipment [Table Text Block] | The following table presents the components of properties and equipment, net of accumulated depreciation, depletion and amortization and assets held-for-sale:  September 30, 2012 December 31, 2011 (in thousands)Properties and equipment, net:   Natural gas and crude oil properties   Proved$1,943,426 $1,694,694Unproved356,235 102,466Total natural gas and crude oil properties2,299,661 1,797,160Pipelines and related facilities42,398 40,721Transportation and other equipment34,230 32,475Land and buildings14,954 14,572Construction in progress84,755 69,633Gross properties and equipment2,475,998 1,954,561Accumulated depreciation, depletion and amortization(742,335) (652,845)Properties and equipment, net$1,733,663 $1,301,716     |

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| - Definition
Tabular disclosure of the useful life and salvage value of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph b -Article 5Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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