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Suspended Wells - Summary of Aging of Suspended Well Costs (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Project
Dec. 31, 2010
Project
Dec. 31, 2009
Project
Dec. 31, 2008
Aging Of Capitalized Exploratory Well Costs [Line Items]        
Exploratory well costs capitalized for a period of one year or less $ 115 $ 220 $ 319  
Exploratory well costs capitalized for a period greater than one year 922 793 589  
Ending balance $ 1,037 $ 1,013 $ 908 $ 660
Number of projects that have exploratory well costs that have been capitalized for a period greater than one year 40 40 34