| **Business Segments (Details) (USD $)In Thousands, unless otherwise specified** | 3 Months Ended | 9 Months Ended |           |
|---------------------------------------------------------------------------------|----------------|----------------|-----------|
||
| **Segment Reporting Information [Line Items]**                                  |           |           |      |   |   |  |
| Number of Operating Segments                                                    |           |           | 2         |   |   |  |
| Revenues                                                                        | $ 41,181       | $ 137,629      | $ 247,572 | $ 296,553 |   |  |
| Segment income (loss) before income taxes:                                      | (50,774)       | 50,086         | (29,804)  | 23,530 |   |  |
| Assets held for sale                                                            | 0              |           | 0         |   | 148,249 | [1] |
| Total Assets                                                                    | 1,931,904      |           | 1,931,904 |   | 1,698,005 | [1] |
| Oil and Gas Properties [Member]                                                 |           |           |      |   |   |  |
| **Segment Reporting Information [Line Items]**                                  |           |           |      |   |   |  |
| Revenues                                                                        | 29,611         | 120,420        | 215,251   | 245,245 |   |  |
| Segment income (loss) before income taxes:                                      | (23,815)       | 73,972         | 49,913    | 99,551 |   |  |
| Total Assets                                                                    | 1,862,131      |           | 1,862,131 |   | 1,461,130 |  |
| Gas Marketing [Member]                                                          |           |           |      |   |   |  |
| **Segment Reporting Information [Line Items]**                                  |           |           |      |   |   |  |
| Revenues                                                                        | 11,570         | 17,209         | 32,321    | 51,308 |   |  |
| Segment income (loss) before income taxes:                                      | (28)           | (19)           | 470       | 880 |   |  |
| Total Assets                                                                    | 7,289          |           | 7,289     |   | 14,713 |  |
| Unallocated [Member]                                                            |           |           |      |   |   |  |
| **Segment Reporting Information [Line Items]**                                  |           |           |      |   |   |  |
| Segment income (loss) before income taxes:                                      | (26,931)       | (23,867)       | (80,187)  | (76,901) |   |  |
| Total Assets                                                                    | 62,484         |           | 62,484    |   | 73,913 |  |
| Assets Held for sale [Member]                                                   |           |           |      |   |   |  |
| **Segment Reporting Information [Line Items]**                                  |           |           |      |   |   |  |
| Assets held for sale                                                            | $ 0            |           | $ 0       |   | $ 148,249 |  |
|                                                                                 |
| [1]Derived from audited 2011 balance sheet.                                     |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Property, plant and equipment that is held for sale apart from normal operations and anticipated to be sold in less than one year.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 46 -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.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.
+ References
Reference 1: 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.(h)(1)(i)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Subparagraph 1(i) -Article 4
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.
+ References
No definition available.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of total revenue for the reportable segments, including revenue from external customers, transactions with other operating segments of the same entity, and (gross) interest revenue. All considered to be "operating revenue" for purposes of the taxonomy.
+ References
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