Leases - Supplemental Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Apr. 30, 2021	Apr. 30, 2020
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 52	$ 50
Right-of-use assets obtained in exchange for new operating lease liabilities	32	328
Right-of-use assets, obtained in exchange for new operating lease liabilities, existing prior to August 1, 2019		$ 319
Right-of-use assets, obtained in exchange for new operating lease liabilities, operating leases not yet commenced	$ 9