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Summary of Short-Term Investments by Geographic Area (Detail) - USD ($)
$ in Thousands
Apr. 28, 2019
Apr. 29, 2018
Schedule of Investments [Line Items]    
Short-term investments $ 0 $ 2,451
Canada [Member]    
Schedule of Investments [Line Items]    
Short-term investments 0 1,366
United States [Member]    
Schedule of Investments [Line Items]    
Short-term investments $ 0 $ 1,085