Stock-Based Compensation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 23, 2015	Jan. 24, 2014	Jan. 23, 2015	Jan. 24, 2014
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	$ 33	$ 33	$ 115	$ 108
Income tax benefits	(8)	(9)	(31)	(30)
Total stock-based compensation expense, net of tax	25	24	84	78
Cost of Products Sold
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	4	3	12	10
Research and Development Expense
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	5	6	20	20
Selling, General and Administrative Expense
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	24	24	83	78
Stock Options
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	7	7	27	27
Restricted Stock Awards
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	24	24	78	72
Employee Stock Purchase Plan
Stock-based Compensation Expense by Component and Classification
Stock-based compensation expense	$ 2	$ 2	$ 10	$ 9