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Fair Value Measurement - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 12 Months Ended
Aug. 31, 2017
Jul. 31, 2017
Apr. 30, 2018
Apr. 30, 2017
Jul. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Reduction in fair value of contingent consideration liability   $ 1,300,000      
Ultimate Survival Technologies, Inc.          
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Contingent consideration payable upon financial performance of acquired business       $ 1,700,000  
Business combination, contingent consideration payable performance period       2 years  
Reduction in fair value of contingent consideration liability     $ 1,600,000    
Business combination contingent consideration liability non-current         $ 60,000
Ultimate Survival Technologies, Inc. | Maximum          
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Contingent consideration payable upon financial performance of acquired business       $ 2,000,000  
Gemini Technologies, Incorporated          
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Business combination, contingent consideration payable performance period 3 years        
Business combination contingent consideration liability non-current         100,000
Contingent consideration maximum payout $ 17,100,000        
(Level 1) | Fair Value on Recurring Basis          
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Cash and cash equivalents     $ 48,900,000   $ 25,200,000