Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	12 Months Ended
	Jul. 25, 2020 USD ($) rating	Jul. 27, 2019 USD ($)	Jul. 28, 2018 USD ($)	Jul. 28, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Average lease term	4 years
Loan receivables term	3 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	$ 900	$ 1,000	$ 1,100
Allowance for future sales returns	79	84
Advertising costs	187	$ 204	$ 166
Right-of-use assets	921
Operating lease liabilities	$ 1,002
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Accounting Standards Update 2016-02
Summary Of Significant Accounting Policies [Line Items]
Right-of-use assets				$ 1,200
Operating lease liabilities				$ 1,200
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