Benefit Plans (Details) $ in Thousands	12 Months Ended
	Apr. 30, 2022 USD ($) executive shares	Apr. 30, 2021 USD ($) shares	Apr. 30, 2020 USD ($)
Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Employer discretionary contribution	$ 10,983	$ 10,382	$ 10,571
Common stock held by trustee of the 401K plan (shares) | shares	807,396	909,161
Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Number of executives covered under SERP | executive	2
Number of executives covered under SERP, retired | executive	1
Annual benefit amount (percent of base compensation)	50.00%
Duration of benefits	20 years
Accrued deferred compensation liability	$ 2,211	$ 2,866
Expected future payments, 2022	637
Expected future payments, 2023	637
Expected future payments, 2024	355
Expected future payments, 2025	355
Expected future payments, 2026	355
Pension and post-retirement expense incurred	$ 18	$ 67	$ 269
Minimum | Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Discount rate	3.35%	1.36%
Maximum | Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Discount rate	4.18%	2.52%