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Employee Benefit Plans (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Employee Benefit Plans (Textual)    
Contributions to pension plans $ 0 $ 0
Pension Plans, Defined Benefit [Member]
    
Components of net periodic benefit cost:    
Service cost 35 23
Interest cost 23 21
Expected return on plan assets (31) (28)
Amortization of:    
Prior service cost (credit) 1 1
Net loss 8 3
Net periodic benefit cost 36 20
Other Postretirement Benefit Plans, Defined Benefit [Member]
    
Components of net periodic benefit cost:    
Service cost 3 3
Interest cost 5 6
Expected return on plan assets 0 0
Amortization of:    
Prior service cost (credit) (5) (6)
Net loss 0 0
Net periodic benefit cost $ 3 $ 3