Supplemental Gas Data Exploratary Wells (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Less than one year	$ 0
More than one year but less than five years	3,309
More than five years	2,171
Total	5,480
Costs expensed due to determination of dry hole or abandonment of project	5,108	9,614	8,194
Costs reclassified to wells, equipment and facilities based on the determination of proved reserves	$ 189	$ 93,482	$ 52,332

The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.

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The amount of exploratory well costs that have been capitalized for a period of greater than one year after the completion of drilling.

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The amount of exploratory well costs that have been capitalized for a period of one year or less after the completion of drilling.

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The amount of capitalized exploratory well costs that have been capitalized for a period greater than or equal to five years after completion of drilling at balance sheet date.

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The adjustment to expense previously capitalized costs of drilling exploratory wells when proved reserves are not found or when the entity obtains information that raises substantial doubt about the economic or operational viability of the project.

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Previously capitalized costs of the drilling of wells that were reclassified as part of the costs of the enterprise's wells and related equipment and facilities at the time that proved reserves were found.

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