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		9 Months Ended
	Jan. 29, 2016	Jan. 23, 2015	Jan. 29, 2016	Jan. 23, 2015
AFS Debt Maturities
Due in one year or less	$ 2,197		$ 2,197
Due after one year through five years	6,294		6,294
Due after five years through ten years	3,050		3,050
Due after ten years	285		285
Total	11,826		11,826
Debt [Member]
AFS Gross Realized Gain (Loss)
Proceeds from sales	1,261	$ 1,478	3,979	$ 4,114
Gross realized gains	2	10	11	26
Gross realized losses	(9)	(4)	(21)	(9)
Impairment losses recognized	0	0	0	0
Equity [Member]
AFS Gross Realized Gain (Loss)
Proceeds from sales	4	208	38	237
Gross realized gains	4	99	36	157
Gross realized losses	0	0	0	0
Impairment losses recognized	$ (2)	$ (1)	(43)	(22)
Equity [Member] | Other expense, net [Member]
AFS Gross Realized Gain (Loss)
Gross realized gains			$ 9	$ 41