Quarterly report pursuant to Section 13 or 15(d)

Components of Stock-Based Compensation Expense Recognized (Detail)

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Components of Stock-Based Compensation Expense Recognized (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Oct. 31, 2015
Oct. 31, 2014
Oct. 31, 2015
Oct. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total stock-based compensation expense, pre-tax $ 5,322 $ 3,640 $ 9,013 $ 6,959
Tax benefit from stock-based compensation expense (1,714) (1,114) (2,868) (2,096)
Total stock-based compensation expense, net of tax 3,608 2,526 6,145 4,863
Restricted Stock        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total stock-based compensation expense, pre-tax 5,178 3,617 8,732 6,869
Stock Options        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total stock-based compensation expense, pre-tax   $ 23 17 $ 90
ESPP        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total stock-based compensation expense, pre-tax $ 144   $ 264