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Accounting For Suspended Exploratory Well Costs (Change In Capitalized Suspended Exploratory Well Costs) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Accounting For Suspended Exploratory Well Costs [Abstract]      
Capitalized exploratory well costs, beginning balance $ 2,893 $ 2,005 $ 1,585
Additions pending the determination of proved reserves 310 1,103 624
Charged to expense (213) (104) (51)
Reclassifications to wells, facilities and equipment based on the determination of proved reserves (149) (136) (200)
Other 40 25 47
Capitalized exploratory well costs, ending balance 2,881 2,893 2,005
Ending balance attributed to equity companies included above     $ 9