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Segment Information - Additional Information (Detail)
$ in Millions
12 Months Ended
Apr. 30, 2017
USD ($)
Customer
Segment
Group
Apr. 30, 2016
USD ($)
Customer
Apr. 30, 2015
USD ($)
Customer
Segment Reporting Information [Line Items]      
Number of major business segments | Segment 3    
Number of major product and service groups | Group 4    
Number of major customers that account more than 10% of total revenues | Customer 0 0 0
International Customers      
Segment Reporting Information [Line Items]      
Total revenue | $ $ 18.8 $ 19.8 $ 16.3
International Customers | Total revenues | Customer Concentration Risk      
Segment Reporting Information [Line Items]      
Percentage of total revenue 18.00% 17.00% 16.00%