Description of Business and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Aug. 01, 2019	Jul. 31, 2019
Capitalized Contract Cost [Line Items]
Net change in customer fund deposits	$ (23)	$ 71
Deferred revenue recognized	$ 355	327
Timing of performance obligation	12 months
Long-term deferred revenue	$ 2			$ 4
Notes receivable	96			95
Operating lease right-of-use assets	307
Present value of lease liabilities	352
Deferred rent liability	$ 0			$ (47)
Accounting Standards Update 2016-02
Capitalized Contract Cost [Line Items]
Operating lease right-of-use assets			$ 319
Present value of lease liabilities			361
Deferred rent liability			47
Prepaid rent			$ 5
Restatement adjustment
Capitalized Contract Cost [Line Items]
Net change in customer fund deposits		$ (71)