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Inventories (Components Of Inventories) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2012
Dec. 31, 2011
Inventories [Abstract]    
Crude oil $ 234 $ 204
Petroleum and chemical products 108 120
Coal and coke   190
Materials, supplies and other 45 73
Total inventories $ 387 $ 587