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, 2018
Dec. 31, 2017
Cost    
Due in one year or less $ 193  
Due after one year through three years 434  
Due after three years through five years 24  
Due after five years 73  
Marketable Securities, Debt Maturities, Amortized Cost, Total 724  
Equity securities 2  
Total Amortized Cost 726 $ 736
Estimated Fair Value    
Due in one year or less 193  
Due after one year through three years 430  
Due after three years through five years 23  
Due after five years 72  
Marketable Securities, Debt Maturities, Fair Value, Total 718  
Equity securities 2  
Total Estimated Fair Value $ 720 $ 749