Goodwill and Acquired Intangible Assets - Acquired Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
Finite-Lived Intangible Assets [Abstract]
Cost	$ 744	$ 742
Accumulated amortization	(716)	(688)
Acquired intangible assets, net	$ 28	$ 54
Weighted average life in years	4 years	4 years
Expected Future Amortization Expense
2021	$ 17
2022	10
2023	1
2024	0
2025	0
Thereafter	0
Acquired intangible assets, net	28	$ 54
Customer Lists
Finite-Lived Intangible Assets [Abstract]
Cost	256	256
Accumulated amortization	(248)	(245)
Acquired intangible assets, net	$ 8	$ 11
Weighted average life in years	5 years	5 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 8	$ 11
Purchased Technology
Finite-Lived Intangible Assets [Abstract]
Cost	421	422
Accumulated amortization	(404)	(383)
Acquired intangible assets, net	$ 17	$ 39
Weighted average life in years	3 years	3 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 17	$ 39
Trade Names and Logos
Finite-Lived Intangible Assets [Abstract]
Cost	25	25
Accumulated amortization	(25)	(24)
Acquired intangible assets, net	0	$ 1
Weighted average life in years		3 years
Expected Future Amortization Expense
Acquired intangible assets, net	0	$ 1
Covenants Not to Compete or Sue
Finite-Lived Intangible Assets [Abstract]
Cost	42	39
Accumulated amortization	(39)	(36)
Acquired intangible assets, net	$ 3	$ 3
Weighted average life in years	3 years	3 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 3	$ 3