Available-for-Sale Debt Investments and Equity Investments (Summary of Available-for-sale Debt Investments and Equity Investments) (Details) - USD ($) $ in Millions	Jan. 26, 2019	Jul. 28, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale debt investments	$ 30,486	$ 37,009
Marketable equity securities	62	605
Total investments	30,548	37,614
Non-marketable equity securities included in other assets (1)	1,133	978
Equity method investments included in other assets	115	118
Total	31,796	38,710
Debt Securities, Available-for-sale [Line Items]
Non-marketable equity securities included in other assets	1,133	$ 978
Net Asset Value (NAV) | Private equity funds
Investments, Debt and Equity Securities [Abstract]
Non-marketable equity securities included in other assets (1)	600
Debt Securities, Available-for-sale [Line Items]
Non-marketable equity securities included in other assets	$ 600