Cash and Cash Equivalents, Investments, and Funds Held for Customers - Classified by the stated maturity date (Details) - USD ($) $ in Millions	Apr. 30, 2019	Jul. 31, 2018
Amortized Cost
Due within one year	$ 330	$ 250
Due within two years	145	117
Due within three years	81	66
Due after three years	44	21
Total available-for-sale debt securities	600	454
Fair Value
Due within one year	330	250
Due within two years	145	116
Due within three years	81	65
Due after three years	44	21
Total available-for-sale debt securities	$ 600	$ 452