Financial Instruments - Activity Related to the Company's Investment Portfolio and Available-for-sale Debt Securities Contractual Maturities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 27, 2017	Oct. 28, 2016	Oct. 27, 2017	Oct. 28, 2016
AFS Debt Maturities
Due in one year or less	$ 865		$ 865
Due after one year through five years	2,601		2,601
Due after five years through ten years	3,298		3,298
Due after ten years	107		107
Total	6,871		6,871
Debt
AFS Gross Realized Gain (Loss)
Proceeds from sales	1,383	$ 2,444	2,354	$ 3,542
Gross realized gains	11	57	19	64
Gross realized losses	(12)	(37)	(15)	(49)
Impairment losses recognized	0	0	0	0
Equity
AFS Gross Realized Gain (Loss)
Proceeds from sales	0	76	0	82
Gross realized gains	0	25	7	29
Gross realized losses	0	0	0	0
Impairment losses recognized	$ (1)	$ (7)	$ (1)	$ (10)