Segment Information and Major Customers (Net Sales for Groups of Similar Products and Services) (Details) (USD $) In Millions	3 Months Ended					9 Months Ended
	Apr. 30, 2011		Apr. 30, 2011	May 01, 2010		Apr. 30, 2011		May 01, 2010
Net sales	$ 10,866	[1]	$ 10,866	$ 10,368	[1]	$ 32,023	[1]	$ 29,204	[1]
Routers [Member]
Net sales	1,860	[1]		1,741	[1]	5,367	[1]	4,965	[1]
Switches [Member]
Net sales	3,299	[1]		3,639	[1]	9,982	[1]	9,871	[1]
New Products [Member]
Net sales	3,262	[1]		2,832	[1]	9,568	[1]	8,149	[1]
Other [Member]
Net sales	248	[1]		224	[1]	688	[1]	627	[1]
Product [Member]
Net sales	8,669	[1]		8,436	[1]	25,605	[1]	23,612	[1]
Service [Member]
Net sales	$ 2,197	[1]		$ 1,932	[1]	$ 6,418	[1]	$ 5,592	[1]

[1] Certain reclassifications have been made to prior period amounts to conform to the current period's presentation.