Derivative Instruments (Effect of Derivative Instruments Designated as Fair Value Hedges and Underlying Hedged Items on Consolidated Statements of Operations) (Details) - Derivatives Designated as Fair Value Hedging Instruments - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Oct. 27, 2018 |
Oct. 28, 2017 |
|
| Hedge Underlying Gain Loss [Line Items] | ||
| GAINS (LOSSES) ON DERIVATIVE INSTRUMENTS | $ (9) | $ (60) |
| GAINS (LOSSES) RELATED TO HEDGED ITEMS | 9 | 60 |
| Interest rate derivatives | Interest expense | ||
| Hedge Underlying Gain Loss [Line Items] | ||
| GAINS (LOSSES) ON DERIVATIVE INSTRUMENTS | (9) | (46) |
| GAINS (LOSSES) RELATED TO HEDGED ITEMS | 9 | 46 |
| Equity derivatives | Other income (loss), net | ||
| Hedge Underlying Gain Loss [Line Items] | ||
| GAINS (LOSSES) ON DERIVATIVE INSTRUMENTS | 0 | (14) |
| GAINS (LOSSES) RELATED TO HEDGED ITEMS | $ 0 | $ 14 |