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Summary of Significant Accounting Policies - Schedule of Activity in Allowance for Doubtful Accounts (Detail) - USD ($)
$ in Thousands
12 Months Ended
Apr. 30, 2019
Apr. 30, 2018
Allowance for Doubtful Accounts Receivable [Roll Forward]    
Balance at beginning of year $ 384 $ 191
Bad debt provision 65 344
Doubtful accounts written off (net) (88) (151)
Balance at end of year $ 361 $ 384