Cash and Cash Equivalents, Investments, and Funds Held for Customers - Classification on Balance Sheets (Details) - USD ($) $ in Millions	Jan. 31, 2021	Jul. 31, 2020	Jan. 31, 2020
Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 1,952	$ 6,442	$ 1,641
Available-for-sale debt securities, amortized cost	981	800
Total cash and cash equivalents, investments, and funds held for customers, amortized cost	3,159	7,497
Cash equivalents:	1,952	6,442
Available-for-sale debt securities, fair value	986	808
Total cash and cash equivalents, investments, and funds held for customers, fair value	3,164	7,505
Investments
Cash and Cash Equivalents Items [Line Items]
Available-for-sale debt securities, amortized cost	781	600
Available-for-sale debt securities, fair value	786	608
Funds held for customers
Cash and Cash Equivalents Items [Line Items]
Available-for-sale debt securities, amortized cost	426	455
Available-for-sale debt securities, fair value	$ 426	$ 455