Goodwill and Acquired Intangible Assets - Acquired Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Finite-Lived Intangible Assets [Abstract]
Cost	$ 724	$ 662
Accumulated amortization	(663)	(640)
Acquired intangible assets, net	$ 61	$ 22
Weighted average life in years	4 years	6 years
Expected Future Amortization Expense
2019	$ 25
2020	22
2021	10
2022	3
2023	1
Thereafter	0
Acquired intangible assets, net	61	$ 22
Customer Lists
Finite-Lived Intangible Assets [Abstract]
Cost	257	240
Accumulated amortization	(242)	(240)
Acquired intangible assets, net	$ 15	0
Weighted average life in years	5 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 15	0
Purchased Technology
Finite-Lived Intangible Assets [Abstract]
Cost	403	367
Accumulated amortization	(364)	(346)
Acquired intangible assets, net	$ 39	$ 21
Weighted average life in years	4 years	6 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 39	$ 21
Trade Names and Logos
Finite-Lived Intangible Assets [Abstract]
Cost	25	23
Accumulated amortization	(24)	(23)
Acquired intangible assets, net	$ 1	0
Weighted average life in years	3 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 1	0
Covenants Not to Compete or Sue
Finite-Lived Intangible Assets [Abstract]
Cost	39	32
Accumulated amortization	(33)	(31)
Acquired intangible assets, net	$ 6	$ 1
Weighted average life in years	3 years	9 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 6	$ 1