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Commitments And Contingencies (Schedule Of Environmental Remediation Activity) (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance - January 1 $ 758 $ 721
Reductions for payments made (61) (54)
Changes in estimates 65 120
Ending balance - September 30 $ 762 $ 787