Fair Value Measurements (Details 1) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Fair Value, Measurements, Nonrecurring [Member]
Values of assets measured at fair value on a nonrecurring basis
Natural gas and oil properties, fair value	$ 24,388	$ 0	$ 24,388	$ 16,075
Natural gas and oil properties, impairment	$ 38,681	$ 0	$ 38,681	$ 6,505

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-Glossary Impairment

-URI http://asc.fasb.org/extlink&oid=6515133

+ Details