Cash and Cash Equivalents, Investments, and Funds Held for Customers - Classification on Balance Sheets (Details) - USD ($) $ in Millions	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2018
Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 1,630	$ 2,116	$ 1,084
Available-for-sale debt securities, amortized cost	821	822
Total cash and cash equivalents, investments, and funds held for customers, Amortized Cost	2,677	3,187
Cash and cash equivalents, fair value	1,630	2,116
Available-for-sale debt securities, fair value	825	824
Total cash and cash equivalents, investments, and funds held for customers, Fair Value	2,681	3,189
Investments
Cash and Cash Equivalents Items [Line Items]
Available-for-sale debt securities, amortized cost	622	622
Available-for-sale debt securities, fair value	625	624
Funds held for customers
Cash and Cash Equivalents Items [Line Items]
Available-for-sale debt securities, amortized cost	412	436
Available-for-sale debt securities, fair value	413	436
Long-term investments
Cash and Cash Equivalents Items [Line Items]
Available-for-sale debt securities, amortized cost	13	13
Available-for-sale debt securities, fair value	$ 13	$ 13