v2.4.0.6
Employee Benefits, Amounts Recognized in Accumulated OCI and Weighted-Average Assumptions in Determining Net Periodic Benefit Cost (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Pension Benefits [Member]
      
Weighted Average Assumptions for Determining Net Periodic Benefit Cost [Abstract]      
Discount rate 5.00% 5.25% 5.75%
Expected return on plan assets 7.50% 8.25% 8.25%
Pension Benefits Qualified [Member]
      
Amounts Recognized in Accumulated Other Comprehensive Income Pre Tax [Abstract]      
Net actuarial loss 3,323 2,699  
Net prior service credit (2) 0  
Net transition obligation 0 0  
Total 3,321 2,699  
Pension Benefits Nonqualified [Member]
      
Amounts Recognized in Accumulated Other Comprehensive Income Pre Tax [Abstract]      
Net actuarial loss 184 137  
Net prior service credit 0 0  
Net transition obligation 0 0  
Total 184 137  
Other benefits [Member]
      
Amounts Recognized in Accumulated Other Comprehensive Income Pre Tax [Abstract]      
Net actuarial loss 19 61  
Net prior service credit (25) (27)  
Net transition obligation 1 1  
Total (5) 35  
Weighted Average Assumptions for Determining Net Periodic Benefit Cost [Abstract]      
Discount rate 4.75% 5.25% 5.75%
Expected return on plan assets 6.00% 6.00% 8.25%