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, 2020	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Amortized Cost
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	$ 6,697	$ 2,352	$ 1,631	$ 701
Total available-for-sale debt securities	800	822
Total cash and cash equivalents, investments, and funds held for customers	7,516	3,187
Fair Value
Total available-for-sale debt securities	808	824
Total cash and cash equivalents, investments, and funds held for customers	7,524	3,189
Total cash, cash equivalents, restricted cash, and restricted cash equivalents
Amortized Cost
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	6,697	2,352
Fair Value
Total cash and cash equivalents	6,697	2,352
Municipal bonds
Amortized Cost
Total available-for-sale debt securities	9	5
Fair Value
Total available-for-sale debt securities	9	5
Corporate notes
Amortized Cost
Total available-for-sale debt securities	744	798
Fair Value
Total available-for-sale debt securities	752	800
U.S. agency securities
Amortized Cost
Total available-for-sale debt securities	47	19
Fair Value
Total available-for-sale debt securities	47	19
Total available-for-sale debt securities
Amortized Cost
Total available-for-sale debt securities	800	822
Fair Value
Total available-for-sale debt securities	808	824
Other long-term investments
Amortized Cost
Other long-term investments	19	13
Fair Value Measurement | Other long-term investments
Amortized Cost
Other long-term investments	$ 19	$ 13