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Financial Instruments - Contractual Maturities of Investments in Available-for-Sale Debt Securities (Details)
$ in Millions
Jan. 31, 2020
USD ($)
Amortized Cost  
Due in one to five years $ 9
Due in more than five years 124
Debt securities, Amortized Cost 133
Fair Value  
Due in one to five years 9
Due in more than five years 146
Debt securities, Fair Value $ 155