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Schedule Of Components Of Net Periodic Benefit Cost (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Pension Benefits
        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 46 $ 41 $ 93 $ 82
Interest cost 160 171 320 340
Expected return on plan assets (201) (202) (403) (403)
Amortization of prior service benefit 4 4 9 9
Recognized net actuarial loss 95 62 191 124
Net periodic benefit cost 104 76 210 152
Other Postretirement Benefits
        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 3 4 7 8
Interest cost 33 39 66 79
Expected return on plan assets       (1)
Amortization of prior service benefit (4) (4) (8) (8)
Recognized net actuarial loss 6 6 12 13
Net periodic benefit cost $ 38 $ 45 $ 77 $ 91