Investments (Marketable Securities, Credit Losses on and Maturities of Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 27, 2012	Jan. 28, 2011	Jan. 27, 2012	Jan. 28, 2011	Apr. 29, 2011
Short-term
Available-for-sale securities, short-term	$ 1,155		$ 1,155		$ 1,046
Trading securities, short-term	0		0		0
Total short-term	1,155		1,155		1,046
Long-term
Available-for-sale securities, long-term	6,549		6,549		5,425
Trading securities, long-term	44		44		39
Total long-term	6,593		6,593		5,464
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning Balance	20	21	20	17
Additional credit losses recognized on securities previously impaired	1	0	1	3
Credit losses recognized on securities previously not impaired	0	0	1	2
Reductions for securities sold during the period	0	(1)	(1)	(2)
Ending Balance	21	20	21	20
AFS Debt Maturities
Due in one year or less	1,705		1,705
Due after one year through five years	5,022		5,022
Due after five years through ten years	607		607
Due after ten years	142		142
Total debt securities	$ 7,476		$ 7,476