Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Apr. 30, 2019
Tax Credit Carryforward [Line Items]
Valuation allowance	$ 4,415	$ 3,630
State [Member]
Tax Credit Carryforward [Line Items]
Gross amount of state tax credit carryforwards	3,900	4,600
Net deferred tax assets related to tax credit carryforwards	600	800
State [Member] | Other Liabilities [Member]
Tax Credit Carryforward [Line Items]
Net deferred tax assets related to tax credit carryforwards	800	1,000
Foreign Tax Authority [Member]
Tax Credit Carryforward [Line Items]
Valuation allowance	500
Gross amount of state tax credit carryforwards	1,200	$ 700
Investment Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Valuation allowance	$ 200