Quarterly report pursuant to Section 13 or 15(d)

Amortized Cost and Estimated Fair Value of Marketable Securities by Contractual Maturity (Detail)

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Amortized Cost and Estimated Fair Value of Marketable Securities by Contractual Maturity (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Cost    
Due in one year or less $ 32  
Due after one year through three years 219  
Due after three years through five years 53  
Due after five years 287  
Marketable Securities, Debt Maturities, Amortized Cost, Total 591  
Equity securities 2  
Total Amortized Cost 593 1,232
Estimated Fair Value    
Due in one year or less 33  
Due after one year through three years 220  
Due after three years through five years 54  
Due after five years 295  
Marketable Securities, Debt Maturities, Fair Value, Total 602  
Equity securities 2  
Total Estimated Fair Value $ 604