Stock-Based Compensation - Summary of Vested Performance Based Restricted Stock Units (Detail) - Performance Based Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Apr. 29, 2018	Apr. 30, 2017	May 01, 2016
NEOs and Key Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Vested	[1]	102,845	37,192	115,855
Weighted Average Fair Value	[1],[2]	$ 1,820	$ 637	$ 1,183
Price Per Share	[1],[3]	$ 17.70	$ 17.12	$ 10.21
Non-employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Vested	[4]	16,000	12,000
Weighted Average Fair Value	[2],[4]	$ 520	$ 345
Price Per Share	[4],[5]	$ 32.50	$ 28.77

[1] NEOs and key employees.

[2] Dollar amounts are in thousands.

[3] Price per share represents closing price of our common stock on the date of grant.

[4] Non-employee

[5] The respective grants vested during the first quarter of fiscal 2018 or 2017, respectively. Accordingly, the price per share represents the closing price of our common stock on the date the award vested.