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
Mar. 31, 2012
Dec. 31, 2011
Cost    
Due in one year or less $ 385  
Due after one year through three years 252  
Due after three years through five years 44  
Due after five years 256  
Marketable Securities, Debt Maturities, Amortized Cost, Total 937  
Equity securities 3  
Total Amortized Cost 940 1,232
Estimated Fair Value    
Due in one year or less 385  
Due after one year through three years 253  
Due after three years through five years 45  
Due after five years 261  
Marketable Securities, Debt Maturities, Fair Value, Total 944  
Equity securities 3  
Total Estimated Fair Value $ 947