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Compensation Related Costs and Share Based Payments - Narrative (Details) - USD ($)
3 Months Ended
Jul. 31, 2021
Jul. 31, 2020
Employee Stock Option    
Share-based Compensation Arrangement by Share-based Payment Award    
Number of shares available for grant reduction per stock option issued (in shares) 1  
Exercised (in shares) 3,000  
Aggregate intrinsic value for exercised options $ 529,000  
Restricted Stock Units    
Share-based Compensation Arrangement by Share-based Payment Award    
Number of shares available for grant reduction per equity instruments other options issued (in shares) 2  
Stock Incentive Plans | Employee Stock Option    
Share-based Compensation Arrangement by Share-based Payment Award    
Unrecognized compensation costs related to plan $ 0  
Stock Incentive Plans | Restricted Stock Units    
Share-based Compensation Arrangement by Share-based Payment Award    
Earnings before interest, tax, depreciation and amortization measurement period 3 years  
Total shareholder return measurement period 3 years  
Return on invested capital measurement period 3 years  
Allocated share-based compensation expense $ 8,623,000 $ 7,021,000
Unrecognized compensation costs related to plan $ 48,980,000  
2018 Stock Plan    
Share-based Compensation Arrangement by Share-based Payment Award    
Number of shares available for grant (in shares) 1,974,386  
2018 Stock Plan | Employee Stock Option    
Share-based Compensation Arrangement by Share-based Payment Award    
Number of options outstanding (in shares) 0  
Prior Plans | Employee Stock Option    
Share-based Compensation Arrangement by Share-based Payment Award    
Number of options outstanding (in shares) 0