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Commitments and Contingencies - Additional Information (Detail) - USD ($)
12 Months Ended
Apr. 30, 2018
Apr. 30, 2017
Apr. 30, 2016
Commitment And Contingencies [Line Items]      
Rental expense for operating leases $ 1,200,000 $ 1,100,000 $ 1,000,000
Employee contribution percentage 60.00%    
Employer profit sharing contribution to 401(k)plan $ 330,000 0 0
Various Operating Leases      
Commitment And Contingencies [Line Items]      
Operating lease rental income 0 236,000 309,000
Headquarters in Atlanta, GA      
Commitment And Contingencies [Line Items]      
Operating lease rental income $ 357,000 $ 538,000 $ 723,000