Financial Instruments - Investments by Category and Related Balance Sheet Classification (Details) - USD ($) $ in Millions	Oct. 26, 2018	Apr. 27, 2018
Schedule of Investments [Line Items]
Cost	$ 6,419	$ 6,963
Unrealized Gains	13	22
Unrealized Losses	(166)	(165)
Fair Value	6,266	6,820
Investments
Schedule of Investments [Line Items]
Fair Value	6,222	6,776
Other Assets
Schedule of Investments [Line Items]
Fair Value	44	44
Level 2
Schedule of Investments [Line Items]
Cost	5,765	6,184
Unrealized Gains	13	22
Unrealized Losses	(137)	(136)
Fair Value	5,641	6,070
Level 2 | Investments
Schedule of Investments [Line Items]
Fair Value	5,641	6,070
Level 2 | Other Assets
Schedule of Investments [Line Items]
Fair Value	0	0
U.S. government and agency securities | Level 1
Schedule of Investments [Line Items]
Cost	607	732
Unrealized Gains	0	0
Unrealized Losses	(26)	(26)
Fair Value	581	706
U.S. government and agency securities | Level 1 | Investments
Schedule of Investments [Line Items]
Fair Value	581	706
U.S. government and agency securities | Level 1 | Other Assets
Schedule of Investments [Line Items]
Fair Value	0	0
U.S. government and agency securities | Level 2
Schedule of Investments [Line Items]
Cost	854	848
Unrealized Gains	0	0
Unrealized Losses	(23)	(24)
Fair Value	831	824
U.S. government and agency securities | Level 2 | Investments
Schedule of Investments [Line Items]
Fair Value	831	824
U.S. government and agency securities | Level 2 | Other Assets
Schedule of Investments [Line Items]
Fair Value	0	0
Corporate debt securities | Level 2
Schedule of Investments [Line Items]
Cost	3,859	4,179
Unrealized Gains	12	20
Unrealized Losses	(76)	(75)
Fair Value	3,795	4,124
Corporate debt securities | Level 2 | Investments
Schedule of Investments [Line Items]
Fair Value	3,795	4,124
Corporate debt securities | Level 2 | Other Assets
Schedule of Investments [Line Items]
Fair Value	0	0
Mortgage-backed securities | Level 2
Schedule of Investments [Line Items]
Cost	502	725
Unrealized Gains	1	2
Unrealized Losses	(34)	(34)
Fair Value	469	693
Mortgage-backed securities | Level 2 | Investments
Schedule of Investments [Line Items]
Fair Value	469	693
Mortgage-backed securities | Level 2 | Other Assets
Schedule of Investments [Line Items]
Fair Value	0	0
Non-U.S. government and agency securities | Level 2
Schedule of Investments [Line Items]
Cost	112	74
Unrealized Gains	0	0
Unrealized Losses	(1)	(1)
Fair Value	111	73
Non-U.S. government and agency securities | Level 2 | Investments
Schedule of Investments [Line Items]
Fair Value	111	73
Non-U.S. government and agency securities | Level 2 | Other Assets
Schedule of Investments [Line Items]
Fair Value	0	0
Other asset-backed securities | Level 2
Schedule of Investments [Line Items]
Cost	438	358
Unrealized Gains	0	0
Unrealized Losses	(3)	(2)
Fair Value	435	356
Other asset-backed securities | Level 2 | Investments
Schedule of Investments [Line Items]
Fair Value	435	356
Other asset-backed securities | Level 2 | Other Assets
Schedule of Investments [Line Items]
Fair Value	0	0
Auction rate securities | Level 3
Schedule of Investments [Line Items]
Cost	47	47
Unrealized Gains	0	0
Unrealized Losses	(3)	(3)
Fair Value	44	44
Auction rate securities | Level 3 | Investments
Schedule of Investments [Line Items]
Fair Value	0	0
Auction rate securities | Level 3 | Other Assets
Schedule of Investments [Line Items]
Fair Value	$ 44	$ 44