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, 2017	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Amortized Cost
Cash and cash equivalents	$ 529	$ 638	$ 808	$ 849
Total cash and cash equivalents, investments, and funds held for customers	1,179	1,411
Fair Value
Total cash and cash equivalents, investments, and funds held for customers	1,180	1,412
Cash and cash equivalents
Amortized Cost
Cash and cash equivalents	529	638
Fair Value
Cash and cash equivalents	529	638
Investments
Amortized Cost
Investments	247	441
Fair Value
Investments	248	442
Funds held for customers
Amortized Cost
Investments	372	304
Fair Value
Investments	372	304
Long-term investments
Amortized Cost
Investments	31	28
Fair Value
Investments	$ 31	$ 28