Quarterly report pursuant to Section 13 or 15(d)

Employee Stock Plans - Additional Information (Detail)

v3.2.0.727
Employee Stock Plans - Additional Information (Detail) - USD ($)
3 Months Ended
Jul. 31, 2015
Jul. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock option grants 0 0
Common stock repurchased, value $ 6,573,000 $ 3,731,000
Shares repurchased during the period 0 0
Time Based Restricted Stock | Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 3 years  
Time Based Restricted Stock | Maximum    
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 300,000  
Total unrecognized compensation cost related to non-vested awards $ 7,800,000  
Performance Based Restricted Stock Unit    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 3 years  
Shares outstanding 200,000  
Total unrecognized compensation cost related to non-vested awards $ 1,900,000  
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 $ 1,100,000 $ 1,500,000
Stock Options | Common Stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock issued for stock options exercised 71,428 85,321
Restricted Stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total unrecognized compensation cost related to non-vested awards $ 31,300,000  
Expected cost recognized over weighted-average period 2 years 8 months 12 days  
Shares repurchased during the period to pay for taxes 188,104 125,421
Common stock repurchased, value $ 6,573,000 $ 3,731,000
Stock Incentive Plan 2008    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Maximum number of shares reserved for issuance 5,700,000  
Issuance of full-value stock awards limitation, required ratio to stock options 1.91  
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 1,600,000  
Employees stock purchased 44,334  
Employees stock purchased, price per share $ 29.55