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Retirement Benefits (Details 6) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Pension Benefits
 
Amounts Expected to be Recognized in 2012 Net Periodic Benefit Cost (Table Amounts) [Abstract]  
Net actuarial loss $ 427
Prior service cost (credit) (58)
Medical and Life Benefits
 
Amounts Expected to be Recognized in 2012 Net Periodic Benefit Cost (Table Amounts) [Abstract]  
Net actuarial loss 21
Prior service cost (credit) $ (51)