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