v2.4.0.6
Employee Benefits, Components of Net Periodic Benefit Cost (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income [Abstract]    
Net actuarial loss (gain) $ (6) $ 5
Total recognized in other comprehensive income (55) (31)
Pension Benefits Qualified [Member]
    
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]    
Service cost 0 0
Interest cost 113 128
Expected return on plan assets (171) (162)
Amortization of net actuarial loss 42 33
Amortization of prior service credit 0 0
Settlement loss 0 1
Net periodic benefit cost (income) (16) 0
Pension Benefits Nonqualified [Member]
    
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]    
Service cost 0 0
Interest cost 7 8
Expected return on plan assets 0 0
Amortization of net actuarial loss 4 3
Amortization of prior service credit 0 0
Settlement loss 4 0
Net periodic benefit cost (income) 15 11
Other benefits [Member]
    
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]    
Service cost 3 3
Interest cost 12 15
Expected return on plan assets (9) (9)
Amortization of net actuarial loss 0 0
Amortization of prior service credit (1) (1)
Settlement loss 0 0
Net periodic benefit cost (income) $ 5 $ 8