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Benefit Plans (Components Of Net Postretirement Health Care Costs) (Details) (Postretirement Benefit Plans [Member], USD $)
In Millions
3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Jun. 30, 2010
Postretirement Benefit Plans [Member]
       
Service cost $ 8 $ 10 $ 18 $ 20
Interest cost 41 44 83 86
Net loss from experience differences 15 14 31 27
Prior service credit (8) (8) (16) (16)
Net periodic benefit cost $ 56 $ 60 $ 116 $ 117