Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Apr. 30, 2025	Apr. 30, 2024	Apr. 30, 2023
Tax Credit Carryforward [Line Items]
Valuation allowance	$ 6,289,000	$ 5,878,000
Income taxes	43,708,000	62,949,000	$ 49,593,000
Payments for renewable energy credits	36,200,000
Refunds received for renewable energy credits	18,900,000
Foreign Tax Jurisdiction [Member]
Tax Credit Carryforward [Line Items]
Valuation allowance	300,000
Gross amount of state tax credit carryforwards	2,600,000	2,400,000
State [Member]
Tax Credit Carryforward [Line Items]
Gross amount of state tax credit carryforwards	3,700,000	3,700,000
Net deferred tax assets related to tax credit carryforwards	100,000	200,000
State [Member] | Other Liabilities [Member]
Tax Credit Carryforward [Line Items]
Deferred Tax Liability, Tax Credit Carryforwards, Net	$ 100,000	$ 200,000