Goodwill and Acquired Intangible Assets - Acquired Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Finite-Lived Intangible Assets [Abstract]
Cost	$ 742	$ 724
Accumulated amortization	(688)	(663)
Acquired intangible assets, net	$ 54	$ 61
Weighted average life in years	4 years	4 years
Expected Future Amortization Expense
2020	$ 28
2021	16
2022	9
2023	1
2024	0
Thereafter	0
Acquired intangible assets, net	54	$ 61
Customer Lists
Finite-Lived Intangible Assets [Abstract]
Cost	256	257
Accumulated amortization	(245)	(242)
Acquired intangible assets, net	$ 11	$ 15
Weighted average life in years	5 years	5 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 11	$ 15
Purchased Technology
Finite-Lived Intangible Assets [Abstract]
Cost	422	403
Accumulated amortization	(383)	(364)
Acquired intangible assets, net	$ 39	$ 39
Weighted average life in years	3 years	4 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 39	$ 39
Trade Names and Logos
Finite-Lived Intangible Assets [Abstract]
Cost	25	25
Accumulated amortization	(24)	(24)
Acquired intangible assets, net	$ 1	$ 1
Weighted average life in years	3 years	3 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 1	$ 1
Covenants Not to Compete or Sue
Finite-Lived Intangible Assets [Abstract]
Cost	39	39
Accumulated amortization	(36)	(33)
Acquired intangible assets, net	$ 3	$ 6
Weighted average life in years	3 years	3 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 3	$ 6