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Employee Retirement Plans - Net Periodic Pension Cost for Defined Benefit Pension Plans (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Qualified Plans [Member]
    
Pension Plans, Postretirement and Other Employee Benefits [Line Items]    
Service cost $ 1 $ 2
Interest cost 10 10
Expected return on plan assets (9) (8)
Amortization of net loss 4 3
Net periodic pension cost 6 7
Non-Qualified Plans [Member]
    
Pension Plans, Postretirement and Other Employee Benefits [Line Items]    
Service cost      
Interest cost 1 1
Expected return on plan assets      
Amortization of net loss 1 1
Net periodic pension cost $ 2 $ 2