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Long-Term Financing Obligations (Parenthetical) (Detail) - USD ($)
9 Months Ended
Jan. 31, 2019
Apr. 30, 2018
Debt Instrument [Line Items]    
Debt Instrument, Face Amount $ 23,000,000  
Debt Instrument Maturity Date Nov. 30, 2020  
Debt Instrument, Unamortized Discount $ 0 $ 104,760
January 31, 2016 through November 30, 2020    
Debt Instrument [Line Items]    
Debt Instrument, Periodic Payment $ 625,000