Leases - Supplemental Balance Sheet (Details) - USD ($) $ in Millions	Apr. 30, 2021	Jul. 31, 2020
Leases [Abstract]
Operating lease right-of-use assets	$ 370	$ 226
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent
Other current liabilities	$ 74	46
Operating lease liabilities	365	221
Total operating lease liabilities	$ 439	$ 267