Stock-Based Compensation Expense in Selling and Administrative Expenses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 27, 2013	Jul. 28, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 4,222	$ 5,040
Selling and administrative expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Restricted stock expense	709	3,628
Restricted stock units expense	4,952	705
Stock option expense	$ (1,439)	$ 707