Cash and Cash Equivalents, Investments, and Funds Held for Customers - Table of cash and cash equivalents, investments, and funds held for customers by balance sheet classification (Details) - USD ($) $ in Millions	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Amortized Cost
Cash and cash equivalents	$ 6,442	$ 2,116	$ 1,464
Investments	800	822
Total cash and cash equivalents, investments, and funds held for customers	7,516	3,187
Fair Value
Investments	808	824
Total cash and cash equivalents, investments, and funds held for customers	7,524	3,189
Cash and cash equivalents
Amortized Cost
Cash and cash equivalents	6,442	2,116
Fair Value
Cash and cash equivalents	6,442	2,116
Investments
Amortized Cost
Investments	600	622
Fair Value
Investments	608	624
Funds held for customers
Amortized Cost
Investments	455	436
Fair Value
Investments	455	436
Long-term investments
Amortized Cost
Investments	19	13
Fair Value
Investments	$ 19	$ 13