Acquisitions and Divestitures - Additional Information (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jan. 23, 2021 USD ($)	Jul. 25, 2020 USD ($) acquisition	Jul. 27, 2019 USD ($)	Jul. 28, 2018 USD ($) acquisition divestiture	Oct. 28, 2018 USD ($)
Divestiture [Line Items]
Number of business combinations (acquisition) | acquisition		6		8
Cash and cash equivalents acquired		$ 23	$ 100
Total purchase consideration		359	2,686	$ 3,200
General and Administrative Expense
Divestiture [Line Items]
Total transaction costs		$ 21	$ 21	$ 41
Forecast | Acacia Communications, Inc.
Divestiture [Line Items]
Cash payments for acquisition	$ 2,600
Disposed of by sale
Divestiture [Line Items]
Number of divestitures (divestiture) | divestiture				2
Disposed of by sale | Service Provider Video Software Solutions Business
Divestiture [Line Items]
Disposal group, tangible assets					$ 160
Disposal group, goodwill and intangible assets					340
Disposal group, liabilities					$ 200