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Stockholders' Equity - Additional Information (Detail)
3 Months Ended 6 Months Ended
Oct. 31, 2020
USD ($)
shares
Oct. 31, 2019
USD ($)
shares
Oct. 31, 2020
USD ($)
OptionPlan
shares
Oct. 31, 2019
USD ($)
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Antidilutive shares excluded from computation of diluted earnings per share 9,052 68,109 9,472  
Number of stock incentive plans | OptionPlan     2  
Intrinsic value of stock outstanding | $ $ 144,400 $ 335,000 $ 144,400 $ 335,000
Intrinsic value of stock exercisable | $ 144,400 335,000 144,400 335,000
Intrinsic value of stock exercised | $ 2,800,000 100,000 2,800,000 100,000
Unrecognized compensation expense relating to outstanding stock options | $ 0 $ 0 0 0
Stock-based compensation expense | $     $ 2,100,000 $ 3,000,000.0
Performance period     3 years  
RSUs        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period     4 years  
Vesting, percentage     0.25%  
Stock units, awarded     234,007 252,911
Grant date fair value of vested RSUs and PSUs | $     $ 6,600,000 $ 1,900,000
Stock units, forfeited       67,454
RSUs | Non-Executive Employees        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock units, awarded     159,485 137,271
RSUs | Executive Officers        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock units, awarded     48,952  
Stock units, forfeited     85,741  
RSUs | Directors        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock units, awarded     25,570 115,640
Performance Shares        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock units, forfeited     92,500 156,725
Performance Shares | Executive Officers        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock units, awarded     36,308  
Stock units, forfeited     92,500  
RSUs and PSUs        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock-based compensation expense | $     $ 1,200,000 $ 2,700,000
Stock units, awarded     270,315 252,911
Stock units, forfeited     178,241 224,179
Unrecognized compensation expense related to unvested RSUs and PSUs | $ $ 4,000,000.0   $ 4,000,000.0  
Weighted average remaining contractual term     1 year 7 months 6 days  
2013 Incentive Stock Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period     4 years  
Stock option, exercisable period     10 years