Stockholders Equity - Stock-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 24, 2014	Oct. 25, 2013	Oct. 24, 2014	Oct. 25, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 67.8	$ 67.6	$ 130.1	$ 133.9
Cost of Product Revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1.6	1.4	3.1	2.7
Cost of Service Revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4.0	4.2	8.4	8.2
Sales and Marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	30.4	31.1	57.4	61.6
Research and Development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	21.2	21.6	42.7	43.0
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 10.6	$ 9.3	$ 18.5	$ 18.4