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Stock-Based Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Long-term stock awards, including restoration options 1,000,000 1,000,000
Total unrecognized compensation expense $ 17 $ 29
Weighted average remaining vesting period in years 2 years 3 years
Total market value (at the vesting date) of stock award shares 32 23
Stock awards granted subsequent to January 1, 2010 have a vesting period, in years five Five
Grant and expire date No Later than 10 years No Later than 10 years
Stock option shares forfeited   2,000,000
Unvested Awards [Member]
    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Total unrecognized compensation expense $ 94 $ 103
Weighted average remaining vesting period in years 4 years 4 years
Stock Option [Member]
    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Stock option shares granted 869,000  
Grant date exercise price per share $ 20  
Stock option shares forfeited 453,070  
Long-Term Stock Awards [Member]
    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Long-term stock awards, including restoration options 1,570,020