Stockholders Equity - Stock-Based Compensation Expense Associated with each Type of Award (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 26, 2012	Oct. 28, 2011	Oct. 26, 2012	Oct. 28, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 65.0	$ 63.0	$ 144.2	$ 121.1
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	11.7	14.7	23.7	29.2
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	43.3	38.9	87.8	73.3
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 10.0	$ 9.4	$ 32.7	$ 18.6