Annual report pursuant to Section 13 and 15(d)

Employee Stock Plans - Additional Information (Detail)

v3.7.0.1
Employee Stock Plans - Additional Information (Detail)
 12 Months Ended
Apr. 30, 2017
USD ($)
$ / shares
shares
Apr. 30, 2016
USD ($)
$ / shares
shares
Apr. 30, 2015
USD ($)
shares
Apr. 30, 2014
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Payments of tax withholdings on restricted stock | $ $ 4,758,000 $ 7,410,000 $ 4,038,000  
Shares repurchased during the period, value | $ $ 33,579,000 $ 7,410,000 $ 4,038,000  
Treasury Stock, Common        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares repurchased during the period 1,140,576 0 0  
Shares repurchased during the period, value | $ $ 28,800,000 $ 0 $ 0  
Time Based Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 4 years      
Market Based Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 3 years      
Shares outstanding 600,000      
Total unrecognized compensation cost related to non-vested awards | $ $ 5,300,000      
Performance Based Restricted Stock Unit        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 3 years      
Shares outstanding 100,000      
Total unrecognized compensation cost related to non-vested awards | $ $ 5,400,000      
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Proceeds from issuance of common stock upon exercise of employee stock options | $ $ 800,000 $ 1,300,000 $ 3,000,000  
Stock Options | Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock issued for stock options exercised 53,955 87,648 178,950  
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares outstanding 1,581,000 1,506,000 1,560,000 1,880,000
Total unrecognized compensation cost related to non-vested awards | $ $ 27,100,000      
Expected cost recognized over weighted-average period 2 years 4 months 24 days      
Shares repurchased during the period to pay for taxes 205,440 215,453    
Payments of tax withholdings on restricted stock | $ $ 4,800,000 $ 7,400,000    
Stock Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock incentive plan, additional number of shares 5,500,000      
Maximum number of shares reserved for issuance 11,200,000      
Issuance of full-value stock awards limitation, required ratio to stock options 2.3      
ESPP        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Maximum number of shares reserved for issuance 3,000,000      
Authorized payroll deductions 15.00%      
Authorized payroll deductions, value | $ $ 25,000      
Fair market price of common stock 85.00%      
Shares available for future issuance 1,300,000      
Employees stock purchased 207,141 95,135 0  
Employees stock purchased, price per share | $ / shares $ 20.93 $ 28.83