Stock-Based Compensation Expense in Selling and Administrative Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 29, 2016	Oct. 31, 2015	Oct. 29, 2016	Oct. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 87	$ 4,792	$ 3,162	$ 7,944
Selling and Administrative Expenses | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	280	150	490	390
Selling and Administrative Expenses | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	(451)	4,278	2,110	6,914
Selling and Administrative Expenses | Performance Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 258	183	$ 562	250
Selling and Administrative Expenses | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense		$ 181		$ 390