Net Changes in Capitalized Exploratory Well Costs (Detail) (USD $) In Thousands	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Beginning balance	$ 497,765	$ 369,862
Additions pending the determination of proved reserves	31,481	89,797
Reclassifications to proved properties based on the determination of proved reserves	0	0
Ending balance	$ 529,246	$ 459,659

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.

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

-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

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