Cash and Cash Equivalents, Investments, and Funds Held for Customers - Table of cash and cash equivalents, investments, and funds held for customers by investment type (Details) - USD ($) $ in Millions	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Amortized Cost
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	$ 2,819	$ 6,697	$ 2,352	$ 1,631
Total available-for-sale debt securities	1,504	800
Total cash and cash equivalents, investments, and funds held for customers	4,323	7,497
Fair Value
Total available-for-sale debt securities	1,508	808
Total cash and cash equivalents, investments, and funds held for customers	4,327	7,505
Total cash, cash equivalents, restricted cash, and restricted cash equivalents
Amortized Cost
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	2,819	6,697
Fair Value
Total cash and cash equivalents	2,819	6,697
Total available-for-sale debt securities
Amortized Cost
Total available-for-sale debt securities	1,504	800
Fair Value
Total available-for-sale debt securities	1,508	808
Municipal bonds
Amortized Cost
Total available-for-sale debt securities	37	9
Fair Value
Total available-for-sale debt securities	38	9
Corporate notes
Amortized Cost
Total available-for-sale debt securities	1,397	744
Fair Value
Total available-for-sale debt securities	1,400	752
U.S. agency securities
Amortized Cost
Total available-for-sale debt securities	70	47
Fair Value
Total available-for-sale debt securities	$ 70	$ 47