Cash and Cash Equivalents, Investments, and Funds Held for Customers - Classified by the stated maturity date (Details) - USD ($) $ in Millions	Oct. 31, 2018	Jul. 31, 2018
Amortized Cost
Due within one year	$ 262	$ 250
Due within two years	119	117
Due within three years	47	66
Due after three years	22	21
Total available-for-sale debt securities	450	454
Fair Value
Due within one year	261	250
Due within two years	118	116
Due within three years	47	65
Due after three years	22	21
Total available-for-sale debt securities	$ 448	$ 452