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Dividend Program (Detail) - USD ($)
3 Months Ended
Aug. 30, 2017
Jun. 13, 2017
Jul. 30, 2017
Jul. 31, 2016
Dividends [Line Items]        
Cash dividends paid     $ 3,608,000 $ 3,445,000
Special Dividend [Member]        
Dividends [Line Items]        
Cash dividend declared, per share   $ 0.21    
Cash dividends paid     $ 2,600,000 $ 2,500,000
Cash dividend payment, per share     $ 0.21 $ 0.21
Quarterly Dividend [Member]        
Dividends [Line Items]        
Cash dividend declared, per share   $ 0.08    
Date of payment to shareholders entitled to dividends   Jul. 17, 2017    
Date of record of shareholders entitled to dividends   Jul. 03, 2017    
Cash dividends paid     $ 1,000,000 $ 861,000
Cash dividend payment, per share     $ 0.08 $ 0.07
Subsequent Event [Member] | Quarterly Dividend [Member]        
Dividends [Line Items]        
Cash dividend declared, per share $ 0.08      
Date of payment to shareholders entitled to dividends Oct. 16, 2017      
Date of record of shareholders entitled to dividends Oct. 02, 2017