XML 85 R21.htm IDEA: XBRL DOCUMENT v2.4.0.8
Postretirement Benefit Plans - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 6 Months Ended 12 Months Ended
Jun. 30, 2013
Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]    
Liability related to funded defined-benefit pension plans $ 358 $ 353
Contributions to benefit plans 0  
Insurance cash value and Rabbi Trust investments supporting supplemental pension plan liability 60 54
Unqualified pension plan liability 60 59
Maximum
    
Defined Benefit Plan Disclosure [Line Items]    
Estimated contributions to benefit plans $ 20