Comprehensive Income - AOCI Components (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 26, 2019	Oct. 27, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 33,571	$ 43,204
Other comprehensive loss	(23)	(201)
Effect of adoption of accounting standards		3,729
Ending balance	34,423	43,848
Net Unrealized Gains (Losses) on Available-for-Sale Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	0	(310)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	87	(8)
(Gains) losses reclassified out of AOCI	(10)	6
Tax benefit (expense)	(9)	13
Other comprehensive loss		11
Effect of adoption of accounting standards		(168)
Ending balance	68	(467)
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(14)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	(1)
(Gains) losses reclassified out of AOCI	0
Tax benefit (expense)	1
Ending balance	(14)
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(11)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.		(4)
(Gains) losses reclassified out of AOCI		0
Tax benefit (expense)		1
Other comprehensive loss		(3)
Effect of adoption of accounting standards		0
Ending balance		(14)
Cumulative Translation Adjustment and Actuarial Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(778)	(528)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	(92)	(207)
(Gains) losses reclassified out of AOCI	1	(1)
Tax benefit (expense)	0	(1)
Other comprehensive loss		(209)
Effect of adoption of accounting standards		0
Ending balance	(869)	(737)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(792)	(849)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	(6)	(219)
(Gains) losses reclassified out of AOCI	(9)	5
Tax benefit (expense)	(8)	13
Other comprehensive loss	(23)	(201)
Effect of adoption of accounting standards		(168)
Ending balance	$ (815)	$ (1,218)