Financial Instruments - Available-For-Sale Securities in Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Oct. 26, 2018	Apr. 27, 2018
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	$ 3,234	$ 4,094
Less than 12 months, Unrealized Losses	(62)	(107)
More than 12 months, Fair Value	1,772	891
More than 12 months, Unrealized Losses	(104)	(58)
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	223	762
Less than 12 months, Unrealized Losses	(8)	(33)
More than 12 months, Fair Value	804	374
More than 12 months, Unrealized Losses	(41)	(17)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	2,538	2,620
Less than 12 months, Unrealized Losses	(47)	(58)
More than 12 months, Fair Value	536	272
More than 12 months, Unrealized Losses	(29)	(17)
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	165	442
Less than 12 months, Unrealized Losses	(5)	(15)
More than 12 months, Fair Value	237	102
More than 12 months, Unrealized Losses	(29)	(19)
Non-U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	42	32
Less than 12 months, Unrealized Losses	0	0
More than 12 months, Fair Value	36	36
More than 12 months, Unrealized Losses	(1)	(1)
Other asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	266	238
Less than 12 months, Unrealized Losses	(2)	(1)
More than 12 months, Fair Value	115	63
More than 12 months, Unrealized Losses	(1)	(1)
Auction rate securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	0	0
Less than 12 months, Unrealized Losses	0	0
More than 12 months, Fair Value	44	44
More than 12 months, Unrealized Losses	$ (3)	$ (3)