v2.4.0.6
Postretirement Benefit Plans - Classification of Pension Plan Assets (Detail) (USD $)
Dec. 31, 2012
Dec. 31, 2011
Level I [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets $ 36 $ 25
Level I [Member] | Equity securities [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 3 1
Level I [Member] | Debt securities [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 20 17
Level I [Member] | Other [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 13 7
Level II [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 110 105
Level II [Member] | Equity securities [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 38 29
Level II [Member] | Debt securities [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 68 71
Level II [Member] | Other [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 4 5
Level III [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets 3 4
Level III [Member] | Equity securities [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets      
Level III [Member] | Debt securities [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets      
Level III [Member] | Other [Member]
   
Major Funded Pension Plans Postretirement And Other Employee Benefits [Line Items]    
Fair value of plan assets $ 3 $ 4