| **Transactions with Affiliates and Other Related Parties** | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
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| **Related Party Transactions [Abstract]**                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Related Party Transactions Disclosure [Text Block]         | TRANSACTIONS WITH AFFILIATES AND OTHER RELATED PARTIES    Affiliated Partnerships. Our Gas Marketing segment markets the natural gas produced by our affiliated partnerships in the Eastern Operating Region. Our sales from natural gas marketing include $0.2 million and $0.4 millionin the three and nine months ended 2012, respectively, related to the marketing of natural gas on behalf of our affiliated partnerships, compared to$0.3 million and $1 million in the three and nine months ended 2011, respectively. Our cost of natural gas marketing includes $0.2 million and $0.4 millionin the three and nine months ended 2012, respectively, compared to$0.3 million and $1 million in the three and nine months ended 2011, respectively, related to these sales.Amounts due from/to the affiliated partnerships are primarily related to derivative positions and, to a lesser extent, unbilled well operating expenses, and costs resulting from audit and tax preparation services. We have entered into derivative instruments on behalf of our 21 affiliated partnerships for a portion of their estimated production. As of September 30, 2012 and December 31, 2011, we had a payable to affiliates of $8.2 million and $14.2 million, respectively, representing their designated portion of the fair value of our gross derivative assets, and a receivable from affiliates of $3.8 million and $6.2 million, respectively, representing their designated portion of the fair value of our gross derivative liabilities.We provide well operations and pipeline services to our affiliated partnerships. The majority of our revenue and expenses related to well operations and pipeline income are associated with services provided to our affiliated partnerships.    PDCM. Our Gas Marketing segment markets the natural gas produced by PDCM. Our sales from natural gas marketing include $2.9 million and $7.5 millionin the three and nine months ended 2012, respectively, related to the marketing of natural gas on behalf of PDCM, compared to$2.6 million and $7.7 million in the three and nine months ended 2011, respectively. Our cost of natural gas marketing includes $2.8 million and $7.3 millionin the three and nine months ended 2012, respectively, compared to$2.5 million and $7.6 million in the three and nine months ended 2011, respectively, related to these sales. We provide certain well operating and administrative services for PDCM. Amounts billed to PDCM for these services were $3 million and $9.2 million in the three and nine months ended 2012, respectively, compared to $2.4 million and $6.9 million in 2011. Our statements of operations include only our proportionate share of these billings. |

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| - Definition
The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39691-107864Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 57 -Paragraph 1-4 -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 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39678-107864Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(k)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph b -Article 3AReference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph k -Article 4
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