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Income Taxes - Additional Information (Detail) - USD ($)
 12 Months Ended
Apr. 30, 2015
Apr. 30, 2014
Apr. 30, 2013
Schedule Of Income Taxes [Line Items]      
Undistributed earning of foreign subsidiaries $ 241,800,000    
Unrecognized tax benefits liability 2,423,000 $ 2,701,000 $ 3,400,000
Unrecognized tax benefits, reductions resulting from resolution (1,400,000)    
Unrecognized tax benefits, accrued interest and penalties 700,000 700,000  
Unrecognized tax benefits, interest 100,000 100,000 $ 0
Internal Revenue Service (IRS)      
Schedule Of Income Taxes [Line Items]      
Net operating loss carryforward $ 5,000,000 $ 12,200,000  
Net operating loss carryforward, beginning expiration 2028    
State and Local Jurisdiction      
Schedule Of Income Taxes [Line Items]      
Net operating loss carryforward $ 21,800,000    
Net operating loss carryforward, beginning expiration 2016    
Foreign Tax Authority      
Schedule Of Income Taxes [Line Items]      
Net operating loss carryforward $ 85,600,000    
Net operating loss carryforward, beginning expiration 2016