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Retirement Plans (Reconciliation Of Benefit Obligations And Plan Or Trust Assets And Resulting Funded Status Of Defined Benefit Retirement Plans) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Pension Benefits [Member]
     
Compensation And Retirement Disclosure Line Items      
Service cost $ (245) $ (211) $ (203)
Interest cost (517) (509) (491)
Funded status at end of year (3,992) (2,988)  
Other Post-Retirement Benefits [Member]
     
Compensation And Retirement Disclosure Line Items      
Service cost (13) (10) (8)
Interest cost (62) (59) (64)
Funded status at end of year (800) (756)  
Change in Benefit Obligation [Member] | Pension Benefits [Member]
     
Compensation And Retirement Disclosure Line Items      
Benefit obligation at beginning of year (9,238) (8,127)  
Service cost (245) (211)  
Interest cost (517) (509)  
Amendments (16) (23)  
Actuarial gain (loss) (670) (736)  
Settlement/curtailment/other (2) (74)  
Benefits paid 446 442  
Benefit obligation at end of year (10,242) (9,238)  
Change in Benefit Obligation [Member] | Other Post-Retirement Benefits [Member]
     
Compensation And Retirement Disclosure Line Items      
Benefit obligation at beginning of year (1,145) (987)  
Service cost (13) (10)  
Interest cost (62) (59)  
Amendments (3) (38)  
Actuarial gain (loss) (40) (126)  
Settlement/curtailment/other 3 (5)  
Benefits paid 81 80  
Benefit obligation at end of year (1,179) (1,145)  
Change in Plan/Trust Assets [Member] | Pension Benefits [Member]
     
Compensation And Retirement Disclosure Line Items      
Fair value of assets at beginning of year 6,250 5,673  
Actual return on plan assets 80 622  
Employer contributions 351 300  
Settlement/curtailment/other 4 69  
Benefits paid (435) (414)  
Fair value of assets at end of year 6,250 6,250  
Change in Plan/Trust Assets [Member] | Other Post-Retirement Benefits [Member]
     
Compensation And Retirement Disclosure Line Items      
Fair value of assets at beginning of year 389 378  
Actual return on plan assets 10 28  
Employer contributions 31 35  
Benefits paid (51) (52)  
Fair value of assets at end of year $ 379 $ 389