Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	3 Months Ended								12 Months Ended
	Jul. 27, 2019 USD ($)	Apr. 27, 2019 USD ($)	Jan. 26, 2019 USD ($)	Oct. 27, 2018 USD ($)	Jul. 28, 2018 USD ($)	Apr. 28, 2018 USD ($)	Jan. 27, 2018 USD ($)	Oct. 28, 2017 USD ($)	Jul. 27, 2019 USD ($) rating	Jul. 28, 2018 USD ($)	Jul. 29, 2017 USD ($)	Oct. 26, 2019 USD ($)	Jul. 28, 2019 USD ($)	Jul. 29, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Average lease term									4 years
Investment credit risk ratings lowest range (credit risk rating) | rating									1
Investment credit risk ratings range highest (credit risk rating) | rating									10
Rating at or higher when receivables deemed impaired (credit risk rating) | rating									8
Threshold for past due receivables									31 days
Threshold for not accruing interest									120 days
Depreciation and amortization expenses									$ 1,000	$ 1,100	$ 1,100
Advertising costs									204	166	209
Revenue	$ 13,428	$ 12,958	$ 12,446	$ 13,072	$ 12,844	$ 12,463	$ 11,887	$ 12,136	51,904	49,330	48,005
Provision (benefit) for income taxes									2,950	12,929	$ 2,678
Retained earnings	(5,903)				1,233				(5,903)	1,233				$ 5,130
Total contract assets noncurrent	481								481
Total capitalized contract acquisition costs	750								750
Capitalized contract acquisition costs, current	416								416
Capitalized contract acquisition costs, noncurrent	334								334
Accounting Standards Update 2014-09
Summary Of Significant Accounting Policies [Line Items]
Retained earnings														2,333
Accounting Standards Update 2016-02 | Forecast | Subsequent event
Summary Of Significant Accounting Policies [Line Items]
Right-of-use assets													$ 1,000
Operating lease liability												$ 1,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Summary Of Significant Accounting Policies [Line Items]
Revenue									1,000
Provision (benefit) for income taxes				$ (152)
Retained earnings														$ 2,300
Software and Service Agreements
Summary Of Significant Accounting Policies [Line Items]
Total contract assets	860				$ 122				860	$ 122
Total contract assets, current	$ 379								$ 379
Maximum
Summary Of Significant Accounting Policies [Line Items]
Loan receivables term									3 years
Financed service contracts term									3 years
Channel partners revolving short-term financing payment term									90 days
End user lease and loan term									3 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Financed service contracts term									1 year
Channel partners revolving short-term financing payment term									60 days