Quarterly report pursuant to Section 13 or 15(d)

Employee Stock Plans - Additional Information (Detail)

v3.3.1.900
Employee Stock Plans - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Oct. 31, 2015
Oct. 31, 2014
Oct. 31, 2015
Oct. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock option grants 0 0 0 0
Common stock repurchased, value     $ 6,596,000 $ 3,748,000
Shares repurchased during the period 0 0 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   300,000  
Total unrecognized compensation cost related to non-vested awards $ 7,600,000   $ 7,600,000  
Performance Based Restricted Stock Unit        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period     3 years  
Shares outstanding 200,000   200,000  
Total unrecognized compensation cost related to non-vested awards $ 1,500,000   $ 1,500,000  
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 $ 100,000 $ 400,000 $ 1,200,000 $ 1,900,000
Stock Options | Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock issued for stock options exercised 9,070 24,308 80,498 109,629
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total unrecognized compensation cost related to non-vested awards $ 28,000,000   $ 28,000,000  
Expected cost recognized over weighted-average period     2 years 6 months  
Shares repurchased during the period to pay for taxes 660 662 188,764 126,083
Common stock repurchased, value $ 100,000 $ 100,000 $ 6,596,000 $ 3,748,000
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   5,700,000  
Issuance of full-value stock awards limitation, required ratio to stock options 1.91   1.91  
ESPP        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Maximum number of shares reserved for issuance 3,000,000   3,000,000  
Authorized payroll deductions 15.00%   15.00%  
Authorized payroll deductions, value     $ 25,000  
Fair market price of common stock     85.00%  
Shares available for future issuance 1,600,000   1,600,000  
Employees stock purchased     44,334  
Employees stock purchased, price per share     $ 29.55