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Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
M
Income Tax Disclosure [Abstract]  
Effective tax rate 18.00%
State income tax benefit $ 12
Time limits for tax audit closings, settlements and expiration of applicable statutes of limitations in various jurisdictions 12
Reduction in the liability for unrecognized tax benefits $ 3