Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (8,778)	$ 2,348	$ (6,384)	$ 4,670
Available-for-sale investments:
Change in net unrealized gains and losses, net of tax benefit (expense) of $1 and $(22) for the three and six months ended January 27, 2018, respectively, and $73 and $154 for the corresponding periods of fiscal 2017, respectively	(191)	(276)	(196)	(397)
Net (gains) losses reclassified into earnings, net of tax (benefit) expense of $15 and $25 for the three and six months ended January 27, 2018, respectively, and $(11) and $(6) for the corresponding periods of fiscal 2017, respectively	(43)	19	(66)	9
Total- Available-for-sale investments	(234)	(257)	(262)	(388)
Cash flow hedging instruments:
Change in unrealized gains and losses, net of tax benefit (expense) of $(2) and $(3) for the three and six months ended January 27, 2018, respectively, and $1 and $4 for the corresponding periods of fiscal 2017, respectively	28	(1)	35	(44)
Net (gains) losses reclassified into earnings, net of tax (benefit) expense of $2 and $4 for the three and six months ended January 27, 2018, respectively, and $(2) and $(3) for the corresponding periods of fiscal 2017, respectively	(16)	25	(27)	36
Total- Cash flow hedging instruments	12	24	8	(8)
Net change in cumulative translation adjustment and actuarial gains and losses net of tax benefit (expense) of $(4) and $(6) for the three and six months ended January 27, 2018, respectively, and $0 and $(1) for the corresponding periods of fiscal 2017, respectively	274	(44)	291	(71)
Other comprehensive income (loss)	52	(277)	37	(467)
Comprehensive income (loss)	(8,726)	2,071	(6,347)	4,203
Comprehensive (income) loss attributable to noncontrolling interests	0	0	0	(8)
Comprehensive income (loss) attributable to Cisco Systems, Inc.	$ (8,726)	$ 2,071	$ (6,347)	$ 4,195