Cash and Cash Equivalents, Investments and Funds Held for Customers - Classified by the stated maturity date (Details) - USD ($) $ in Millions	Oct. 31, 2017	Jul. 31, 2017
Available-for-sale Securities, Debt Maturities
Due within one year, amortized cost	$ 197	$ 209
Due within one year, fair value	197	209
Due within two years, amortized cost	162	164
Due within two years, fair value	162	164
Due within three years, amortized cost	70	59
Due within three years, fair value	70	60
Due after three years, amortized cost	34	30
Due after three years, fair value	34	30
Total available-for-sale debt securities, amortized cost	463	462
Total available-for-sale debt securities, fair value	$ 463	$ 463