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Fair Value Measurement - Additional Information (Detail) - USD ($)
Oct. 31, 2020
Apr. 30, 2020
(Level 1) | Fair Value on Recurring Basis    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents $ 55,500,000 $ 125,000,000.0
(Level 2)    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Financial assets 0  
Financial liabilities 0  
(Level 3)    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Financial assets 0  
Financial liabilities $ 0