Cash and Cash Equivalents, Investments, and Funds Held for Customers - Classification on Balance Sheets (Details) - USD ($) $ in Millions	Apr. 30, 2021	Jul. 31, 2020	Apr. 30, 2020
Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 3,164	$ 6,442	$ 3,371
Available-for-sale debt securities, amortized cost	1,147	800
Total cash and cash equivalents, investments, and funds held for customers, amortized cost	4,459	7,497
Cash equivalents:	3,164	6,442
Available-for-sale debt securities, fair value	1,152	808
Total cash and cash equivalents, investments, and funds held for customers, fair value	4,464	7,505
Investments
Cash and Cash Equivalents Items [Line Items]
Available-for-sale debt securities, amortized cost	948	600
Available-for-sale debt securities, fair value	952	608
Funds held for customers
Cash and Cash Equivalents Items [Line Items]
Available-for-sale debt securities, amortized cost	347	455
Available-for-sale debt securities, fair value	$ 348	$ 455