Supplemental Gas Data Average Unit Prices (Details)	12 Months Ended
Dec. 31, 2011 MMcf	Dec. 31, 2010	Dec. 31, 2009
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume	89.8
Proved Developed and Undeveloped Reserves, Production	153,504,000	127,875,000	94,415,000
Natural Gas, Per Thousand Cubic Feet [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Average gas sales price before effects of financial settlements (per thousand cubic feet)	4,270	4,530	4,150
Average effects of financial settlements (per thousand cubic feet)	630	1,300	2,530
Average gas sales price including effects of financial settlements (per thousand cubic feet)	4,900	5,830	6,680
Average lifting costs, excluding ad valorem and severance taxes (per thousand cubic feet)	.68	.5	.48

Average effects of financial settlements (per thousand cubic feet)

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- Definition

Average gas sales price including effects of financial settlements (per thousand cubic feet)

+ References

No definition available.

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- Definition

Summary of significant aspects of production costs of the energy source on a per unit basis. This information is presented in different formats, including certain specific costs, summarized costs or costs in total.

+ References

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

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 3

-Subparagraph A

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- Definition

The revenues derived from sales of oil or gas in each geographic area during the reporting period divided by the number of barrels of oil produced or thousands of cubic feet of gas produced.

+ References

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

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 3

-Subparagraph A

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- Definition

Total amount of product committed to be supplied under existing contracts or agreements.

+ References

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-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 8

-Subparagraph A

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- Definition

Production of proved reserves.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59F

-Subparagraph e

-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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-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 5

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=6821537&loc=d3e61831-109447

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