Comprehensive Income (Loss) (AOCI components) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Apr. 28, 2018	Jul. 28, 2018	Jul. 29, 2017	Jul. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		$ 66,137
Other comprehensive income (loss)		(940)	$ 373	$ (397)
Effect of adoption of accounting standards		9
Balance, end of period		43,204	66,137
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	310
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.		(543)	(164)	151
(Gains) losses reclassified out of AOCI		(287)	87	1
Tax benefit (expense)		93	37	(49)
Other comprehensive income (loss)		(737)	(40)	103
Effect of adoption of accounting standards		54
Balance, end of period		(310)	373	413
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		32	(59)	(16)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.		21	22	(66)
(Gains) losses reclassified out of AOCI		(68)	79	20
Tax benefit (expense)		4	(10)	3
Other comprehensive income (loss)		(43)	91	(43)
Effect of adoption of accounting standards		0
Balance, end of period		(11)	32	(59)
Cumulative Translation Adjustment and Actuarial Gains and Losses
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		(359)	(680)	(233)
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.		(159)	318	(399)
(Gains) losses reclassified out of AOCI		7	16	(6)
Tax benefit (expense)		(8)	(13)	(42)
Other comprehensive income (loss)		(160)	321	(447)
Effect of adoption of accounting standards		(9)
Balance, end of period		(528)	(359)	(680)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		46	(326)	61
Other comprehensive income (loss) before reclassifications attributable to Cisco Systems, Inc.		(681)	176	(314)
(Gains) losses reclassified out of AOCI		(348)	182	15
Tax benefit (expense)		89	14	(88)
Other comprehensive income (loss)		(940)	372	(387)
Effect of adoption of accounting standards	$ 45	45
Balance, end of period		$ (849)	$ 46	$ (326)