Derivatives and Currency Exchange Risk Management - Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Jan. 25, 2019	Apr. 27, 2018
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 253	$ 79
Derivative liabilities	39	238
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	16	39
Derivative liabilities	$ 15	$ 20