Cash and Cash Equivalents, Investments, and Funds Held for Customers - Classified by the stated maturity date (Details) - USD ($) $ in Millions	Jan. 31, 2018	Jul. 31, 2017
Available-for-sale Securities, Debt Maturities
Due within one year, amortized cost	$ 208	$ 209
Due within one year, fair value	208	209
Due within two years, amortized cost	158	164
Due within two years, fair value	157	164
Due within three years, amortized cost	69	59
Due within three years, fair value	68	60
Due after three years, amortized cost	30	30
Due after three years, fair value	30	30
Total available-for-sale debt securities, amortized cost	465	462
Total available-for-sale debt securities, fair value	$ 463	$ 463