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Industry Segments - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Oct. 31, 2012
Oct. 31, 2013
Customer
Oct. 31, 2012
Apr. 30, 2013
Segment Reporting Information [Line Items]        
Number of major business segments   3    
Number of major product and service groups   4    
Home Depot
       
Segment Reporting Information [Line Items]        
Number of major customers   1    
Percentage of total revenue 10.60% 10.00% 12.20%  
Total revenue $ 2.8 $ 5.0 $ 6.4  
Accounts receivable balance   $ 1.1   $ 1.6