Goodwill and Acquired Intangible Assets - Acquired Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Finite-Lived Intangible Assets [Abstract]
Cost	$ 662	$ 665
Accumulated amortization	(640)	(621)
Acquired intangible assets, net	$ 22	$ 44
Weighted average life in years	6 years	6 years
Expected Future Amortization Expense
2018	$ 13
2019	6
2020	3
2021	0
2022	0
Thereafter	0
Acquired intangible assets, net	22	$ 44
Customer Lists
Finite-Lived Intangible Assets [Abstract]
Cost	240	241
Accumulated amortization	(240)	(240)
Acquired intangible assets, net	0	$ 1
Weighted average life in years		5 years
Expected Future Amortization Expense
Acquired intangible assets, net	0	$ 1
Purchased Technology
Finite-Lived Intangible Assets [Abstract]
Cost	367	369
Accumulated amortization	(346)	(329)
Acquired intangible assets, net	$ 21	$ 40
Weighted average life in years	6 years	6 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 21	$ 40
Trade Names and Logos
Finite-Lived Intangible Assets [Abstract]
Cost	23	23
Accumulated amortization	(23)	(23)
Acquired intangible assets, net	0	0
Expected Future Amortization Expense
Acquired intangible assets, net	0	0
Covenants Not to Compete or Sue
Finite-Lived Intangible Assets [Abstract]
Cost	32	32
Accumulated amortization	(31)	(29)
Acquired intangible assets, net	$ 1	$ 3
Weighted average life in years	9 years	9 years
Expected Future Amortization Expense
Acquired intangible assets, net	$ 1	$ 3