Comprehensive Income (Loss) (AOCI components) (Details) - USD ($) $ in Millions	6 Months Ended
	Jan. 27, 2018	Jan. 28, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	$ 66,137
Balance, end of period	51,982
Net Unrealized Gains (Losses) on Available-for-Sale Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	373	$ 413
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	(174)	(559)
(Gains) losses reclassified out of AOCI	(91)	15
Tax benefit (expense)	3	148
Balance, end of period	111	17
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	32	(59)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	38	(48)
(Gains) losses reclassified out of AOCI	(31)	39
Tax benefit (expense)	1	1
Balance, end of period	40	(67)
Cumulative Translation Adjustment and Actuarial Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	(359)	(680)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	292	(69)
(Gains) losses reclassified out of AOCI	5	(1)
Tax benefit (expense)	(6)	(1)
Balance, end of period	(68)	(751)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	46	(326)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.	156	(676)
(Gains) losses reclassified out of AOCI	(117)	53
Tax benefit (expense)	(2)	148
Balance, end of period	$ 83	$ (801)