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Accounts Receivable - Allowance for Doubtful Accounts (Detail) - Allowance for doubtful accounts [Member] - USD ($)
$ in Thousands
9 Months Ended
Jan. 29, 2017
Jan. 31, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]    
Beginning balance $ (1,088) $ (851)
Provision for bad debts 239 (93)
Net write-offs, net of recoveries 452 130
Ending balance $ (397) $ (814)