Stock-Based Compensation (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
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	$ 34	$ 34	$ 119	$ 124
Income tax benefits	(10)	(9)	(34)	(35)
Total stock-based compensation expense, net of tax	24	25	85	89
Cost of Products Sold
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	3	3	10	10
Research and Development Expense
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	7	6	24	22
Selling, General and Administrative Expense
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	24	25	85	92
Stock Options
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	9	12	36	48
Restricted Stock Awards
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	23	19	74	66
Employee Stock Purchase Plan
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	$ 2	$ 3	$ 9	$ 10