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, 2019	Jul. 31, 2018
Amortized Cost
Due within one year	$ 415	$ 250
Due within two years	208	117
Due within three years	163	66
Due after three years	36	21
Total available-for-sale debt securities	822	454
Fair Value
Due within one year	416	250
Due within two years	208	116
Due within three years	164	65
Due after three years	36	21
Total available-for-sale debt securities	$ 824	$ 452