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
Sep. 30, 2013
Dec. 31, 2012
Cost    
Due in one year or less $ 918  
Due after one year through three years 424  
Due after three years through five years 25  
Due after five years 100  
Marketable Securities, Debt Maturities, Amortized Cost, Total 1,467  
Equity securities 2  
Total Amortized Cost 1,469 587
Estimated Fair Value    
Due in one year or less 918  
Due after one year through three years 424  
Due after three years through five years 24  
Due after five years 98  
Marketable Securities, Debt Maturities, Fair Value, Total 1,464  
Equity securities 3  
Total Estimated Fair Value $ 1,467