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Goodwill And Intangible Assets - Additional Information (Detail) - USD ($)
$ in Millions
 12 Months Ended
Apr. 30, 2015
Apr. 30, 2014
Apr. 30, 2013
Schedule Of Goodwill And Intangible Assets [Line Items]      
Amortization expense $ 8.2 $ 8.7 $ 5.0
Amortizable intangible assets fully amortization year 2031    
Trademarks      
Schedule Of Goodwill And Intangible Assets [Line Items]      
Intangible assets acquired $ 0.3    
Weighted-Average Amortization Period (in years) 1 year    
Customer Lists      
Schedule Of Goodwill And Intangible Assets [Line Items]      
Intangible assets acquired $ 6.2    
Weighted-Average Amortization Period (in years) 10 years    
Non-compete Agreements      
Schedule Of Goodwill And Intangible Assets [Line Items]      
Intangible assets acquired $ 0.1    
Weighted-Average Amortization Period (in years) 5 years