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Employee Retirement Plans - Net Periodic Pension Cost for Defined-Benefit Pension Plans (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Qualified Plans [Member]
     
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Service cost $ 2 $ 2 $ 3
Interest cost 42 44 45
Expected return on plan assets (31) (33) (34)
Recognized prior service cost     (1)
Recognized net loss 14 10 10
Net periodic pension cost 27 23 23
Non-Qualified Plans [Member]
     
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Service cost         
Interest cost 7 8 9
Expected return on plan assets         
Recognized prior service cost         
Recognized net loss 2 1  
Net periodic pension cost $ 9 $ 9 $ 9