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Common Stock Repurchase Program (Detail) - USD ($)
 6 Months Ended
Oct. 28, 2018
Oct. 29, 2017
Jun. 15, 2016
Stockholders Equity Note [Line Items]      
Cost of common stock repurchase $ 844,000    
Common Stock [Member]      
Stockholders Equity Note [Line Items]      
Common stock repurchased 36,880    
Cost of common stock repurchase $ 2,000    
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
Common stock repurchased 36,880 0  
Cost of common stock repurchase $ 844,000    
Remaining authorized repurchase amount $ 4,200,000