Stockholders Equity - Schedule of Employee Stock Purchase Plan ESPP (Detail) (Employee Stock Purchase Plan, USD $) In Millions, except Per Share data, unless otherwise specified	6 Months Ended
	Oct. 25, 2013	Oct. 26, 2012
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per right granted	$ 10.53	$ 10.25
Shares issued under the ESPP	2.0	1.9
Proceeds from issuance of shares	$ 49.9	$ 48.2