Investments (Realized Net Gains (Losses) Related To Available-For-Sale Investments) (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Oct. 29, 2016 |
Oct. 24, 2015 |
|
| Schedule of Investments [Line Items] | ||
| Total | $ 15 | $ (1) |
| Net gains/(losses) on investments in publicly traded equity securities | ||
| Schedule of Investments [Line Items] | ||
| Total | 5 | (9) |
| Net gains/(losses) on investments in fixed income securities | ||
| Schedule of Investments [Line Items] | ||
| Total | $ 10 | $ 8 |