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
Sep. 30, 2017
Dec. 31, 2016
Cost    
Due in one year or less $ 218  
Due after one year through three years 443  
Due after three years through five years 18  
Due after five years 75  
Marketable Securities, Debt Maturities, Amortized Cost, Total 754  
Equity securities 243  
Total Amortized Cost 997 $ 1,083
Estimated Fair Value    
Due in one year or less 218  
Due after one year through three years 442  
Due after three years through five years 18  
Due after five years 76  
Marketable Securities, Debt Maturities, Fair Value, Total 754  
Equity securities 289  
Total Estimated Fair Value $ 1,043 $ 1,091