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Fair Value Measurement - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Aug. 31, 2017
Apr. 30, 2018
Apr. 30, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Reduction in fair value of contingent consideration liability   $ 1,640,000  
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 $ 61,500,000