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, 2013
Dec. 31, 2012
Cost    
Due in one year or less $ 832  
Due after one year through three years 413  
Due after three years through five years 23  
Due after five years 117  
Marketable Securities, Debt Maturities, Amortized Cost, Total 1,385  
Equity securities 2  
Total Amortized Cost 1,387 587
Estimated Fair Value    
Due in one year or less 833  
Due after one year through three years 412  
Due after three years through five years 22  
Due after five years 115  
Marketable Securities, Debt Maturities, Fair Value, Total 1,382  
Equity securities 2  
Total Estimated Fair Value $ 1,384