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
Jun. 30, 2017
Dec. 31, 2016
Cost    
Due in one year or less $ 410  
Due after one year through three years 431  
Due after three years through five years 19  
Due after five years 111  
Marketable Securities, Debt Maturities, Amortized Cost, Total 971  
Equity securities 89  
Total Amortized Cost 1,060 $ 1,083
Estimated Fair Value    
Due in one year or less 410  
Due after one year through three years 428  
Due after three years through five years 19  
Due after five years 113  
Marketable Securities, Debt Maturities, Fair Value, Total 970  
Equity securities 90  
Total Estimated Fair Value $ 1,060 $ 1,091