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, 2013
Dec. 31, 2012
Cost    
Due in one year or less $ 340  
Due after one year through three years 247  
Due after three years through five years 59  
Due after five years 221  
Marketable Securities, Debt Maturities, Amortized Cost, Total 867  
Equity securities 2  
Total Amortized Cost 869 587
Estimated Fair Value    
Due in one year or less 341  
Due after one year through three years 248  
Due after three years through five years 59  
Due after five years 226  
Marketable Securities, Debt Maturities, Fair Value, Total 874  
Equity securities 2  
Total Estimated Fair Value $ 876