Leases - Narrative (Details) $ in Millions	1 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($)	Jul. 31, 2020 USD ($) option_to_extend	Jul. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease terms		10 years
Number of options to extend | option_to_extend		1
Option to extend operating leases		10 years
Operating sublease terms		5 years
Reduction of lease liability	$ 61
Reduction of right-of-use asset	$ 61
Sublease rent expense			$ 42	$ 38
Sublease rental income			$ 24	$ 23
Leases not yet commenced		$ 72
Minimum
Lessee, Lease, Description [Line Items]
Terms for leases not yet commenced		3 years
Maximum
Lessee, Lease, Description [Line Items]
Terms for leases not yet commenced		11 years