Financing Arrangements, 2013 Senior Convertible Notes (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	Apr. 30, 2006
Debt [Line Items]
Common stock settled for warrants in future (in shares)	41		41
Warrants exercise price (per unit)	76.56		76.56
Equity and Debt Information
Net carrying amount	$ 7,314		$ 7,314		$ 7,359
2013 Senior Convertible Notes
Equity and Debt Information
Carrying amount of the equity component	547		547		547
Principal amount	2,200	2,200	2,200	2,200	2,200	2,200
Unamortized discount	(20)		(20)		(90)
Net carrying amount	2,180		2,180		2,110
Stated interest rate						1.625%
Interest Rate and Interest Expense Amounts
Effective interest rate	6.03%	6.03%	6.03%	6.03%
Interest cost related to contractual interest coupon	9	9	27	27
Interest cost related to amortization of the discount	$ 23	$ 22	$ 69	$ 65