Common Stock Repurchase Program (Detail) - USD ($)	12 Months Ended
	Apr. 29, 2018	Apr. 30, 2017	May 01, 2016	Jun. 15, 2016
Stockholders Equity Note [Line Items]
Cost of common stock repurchased			$ 2,397,000
Common Stock [Member]
Stockholders Equity Note [Line Items]
Common stock repurchased	0	0	100,776
Cost of common stock repurchased			$ 5,000
Common Stock Repurchase Program June 15, 2016 [Member] | Common Stock [Member]
Stockholders Equity Note [Line Items]
Authorization amount for repurchase of common stock				$ 5,000,000
Remaining authorized repurchase amount	$ 5,000,000