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Retirement Benefits - Additional Information (Detail) - USD ($)
12 Months Ended
Apr. 30, 2023
Apr. 30, 2022
Defined Benefit Plan Disclosure [Line Items]    
Defined pension benefit plan, net periodic benefit cost $ 580,000  
Anticipated contribution in the next fiscal year related to pension plans 0  
Employer contributions $ 0 $ 0
Increase decrease in the discount rate 1.00% 1.00%
(Decrease) increase pension expense $ 181,000 $ 207,000
Age limit of employees to be eligible for contribution (in years) 21 years  
Minimum service period of employees to be eligible for contribution (in months) 3 months  
Employee's compensation (as a percent) 3.00%  
Employer matching contributions $ 932,000 $ 967,000
Maximum    
Defined Benefit Plan Disclosure [Line Items]    
Matching contributions by company (as a percent) 100.00%  
Contributions by employer per employee's compensation (as a percent) 3.00%  
Employee's compensation (as a percent) 4.00%  
Minimum    
Defined Benefit Plan Disclosure [Line Items]    
Matching contributions by company (as a percent) 50.00%  
Contributions by employer per employee's compensation (as a percent) 5.00%  
Equity Securities | Maximum    
Defined Benefit Plan Disclosure [Line Items]    
Defined benefit plan, Plan asset percentage 75.00% 75.00%
Fixed Income | Maximum    
Defined Benefit Plan Disclosure [Line Items]    
Defined benefit plan, Plan asset percentage 25.00% 25.00%
Yield Curve Technique    
Defined Benefit Plan Disclosure [Line Items]    
Increase decrease in the discount rate 1.00% 1.00%
(Decrease) increase pension expense $ 231,000 $ 271,000
Yield Curve Technique | Pension Plan    
Defined Benefit Plan Disclosure [Line Items]    
Par amount outstanding $ 250,000,000