Stockholders Equity - Stock-Based Compensation Expense Associated with each Type of Award (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 25, 2013	Jan. 27, 2012	Jan. 25, 2013	Jan. 27, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 67.3	$ 76.7	$ 211.5	$ 197.8
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	10.9	13.8	34.6	43.0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	46.3	42.1	134.1	115.4
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 10.1	$ 20.8	$ 42.8	$ 39.4