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Significant Accounting Policies (Detail) - USD ($)
3 Months Ended
Jul. 30, 2017
Jul. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]    
Income taxes $ 1,640,000 $ 3,233,000
Accrued expenses and deferred compensation, operating activities (4,704,000) (4,631,000)
Common stock surrendered for withholding taxes payable, financing activities 1,135,000 280,000
ASU No. 2016-09 [Member]    
New Accounting Pronouncements or Change in Accounting Principle [Line Items]    
Income taxes $ (554,000)  
Excess tax benefit related to stock-based compensation, operating activities   167,000
Excess tax benefit related to stock-based compensation, financing activities   167,000
Accrued expenses and deferred compensation, operating activities   280,000
Common stock surrendered for withholding taxes payable, financing activities   $ 280,000