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, 2019	Jul. 31, 2018	Jul. 31, 2017
Amortized Cost
Cash and cash equivalents	$ 2,116	$ 1,464	$ 529
Investments	822	454
Total cash and cash equivalents, investments, and funds held for customers	3,187	2,098
Fair Value
Investments	824	452
Total cash and cash equivalents, investments, and funds held for customers	3,189	2,096
Cash and cash equivalents
Amortized Cost
Cash and cash equivalents	2,116	1,464
Fair Value
Cash and cash equivalents	2,116	1,464
Investments
Amortized Cost
Investments	622	253
Fair Value
Investments	624	252
Funds held for customers
Amortized Cost
Investments	436	368
Fair Value
Investments	436	367
Long-term investments
Amortized Cost
Investments	13	13
Fair Value
Investments	$ 13	$ 13