Cash and Cash Equivalents, Investments, and Funds Held for Customers - Table of available-for-sale debt securities classified by maturity date (Details) - USD ($) $ in Millions	Jul. 31, 2020	Jul. 31, 2019
Amortized Cost
Due within one year	$ 389	$ 415
Due within two years	256	208
Due within three years	137	163
Due after three years	18	36
Total available-for-sale debt securities	800	822
Fair Value
Due within one year	390	416
Due within two years	261	208
Due within three years	139	164
Due after three years	18	36
Total available-for-sale debt securities	$ 808	$ 824