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. 25, 2013	Jan. 27, 2012	Jan. 25, 2013	Jan. 27, 2012	Apr. 27, 2012
Short-term
Available-for-sale securities, short-term	$ 1,166		$ 1,166		$ 1,344
Trading securities, short-term	0		0		0
Total short-term	1,166		1,166		1,344
Long-term
Available-for-sale securities, long-term	8,786		8,786		7,151
Trading securities, long-term	49		49		46
Total long-term	8,835		8,835		7,197
Credit Loss Portion of Other-than-temporary Impairments on Debt Securities
Beginning Balance	20	20	20	20
Additional credit losses recognized on securities previously impaired	0	1	0	1
Credit losses recognized on securities previously not impaired	0	0	0	1
Reductions for securities sold during the period	(2)	0	(2)	(1)
Ending Balance	18	21	18	21
AFS Debt Maturities
Due in one year or less	1,681		1,681
Due after one year through five years	6,898		6,898
Due after five years through ten years	1,010		1,010
Due after ten years	130		130
Total debt securities	$ 9,719		$ 9,719