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Segment Information - Additional Information (Detail)
$ in Millions
12 Months Ended
Apr. 30, 2015
USD ($)
Customer
Segment
Group
Apr. 30, 2014
USD ($)
Customer
Apr. 30, 2013
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 | Customer 0 0 1
Accounts receivable from major customer     $ 1.6
Consolidated revenues | Customer Concentration Risk      
Segment Reporting Information [Line Items]      
Percentage of total revenue     11.00%
Total revenues | Customer Concentration Risk | Maximum      
Segment Reporting Information [Line Items]      
Percentage of total revenue 10.00% 10.00%  
International Customers      
Segment Reporting Information [Line Items]      
Total revenue $ 16.3 $ 17.1 $ 14.0
International Customers | Consolidated revenues | Customer Concentration Risk      
Segment Reporting Information [Line Items]      
Percentage of total revenue 16.00% 17.00% 14.00%