Cash and Cash Equivalents, Investments, and Funds Held for Customers - Type of issue (Details) - USD ($) $ in Millions	Apr. 30, 2021	Jul. 31, 2020	Apr. 30, 2020	Jul. 31, 2019
Cash and Cash Equivalents Items [Line Items]
Total cash, cash equivalents, restricted cash, and restricted cash equivalents at end of period	$ 3,312	$ 6,697	$ 3,560	$ 2,352
Available-for-sale securities:
Available-for-sale debt securities, amortized cost	1,147	800
Available-for-sale debt securities:	1,152	808
Total cash and cash equivalents, investments, and funds held for customers, amortized cost	4,459	7,497
Total cash and cash equivalents, investments, and funds held for customers, fair value	4,464	7,505
Total cash, cash equivalents, restricted cash, and restricted cash equivalents
Cash and Cash Equivalents Items [Line Items]
Total cash, cash equivalents, restricted cash, and restricted cash equivalents at end of period	3,312	6,697
Cash, cash equivalents, restricted cash, and restricted cash equivalents, fair value	3,312	6,697
Municipal bonds
Available-for-sale securities:
Available-for-sale debt securities, amortized cost	34	9
Available-for-sale debt securities:	34	9
Corporate notes
Available-for-sale securities:
Available-for-sale debt securities, amortized cost	1,057	744
Available-for-sale debt securities:	1,061	752
U.S. agency securities
Available-for-sale securities:
Available-for-sale debt securities, amortized cost	56	47
Available-for-sale debt securities:	$ 57	$ 47