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Description of the deferred compensation arrangement, including fixed amounts and determinable awards, or the method for determining payments and awards, the timing of such payments and awards, and any requisite service or performance criteria, as of the balance sheet date.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Number of options vested.

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Number of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

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Number, after forfeiture, of shares or units issued under share-based payment arrangement. Excludes shares or units issued under employee stock ownership plan (ESOP).

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Number, before forfeiture, of shares issued under share-based payment arrangement. Excludes employee stock ownership plan (ESOP).

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Number of share options (or share units) exercised during the current period.

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Employee Benefit Plans (Details) - USD ($)	12 Months Ended
Employee Benefit Plans (Details) - USD ($)	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 1990
Employee Benefit Plans (Details) [Line Items]
Stock Issued During Period, Value, Employee Benefit Plan (in Dollars)	$ 419,000	$ 417,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	615,000	1,059,500	1,499,750
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	537,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in Dollars per share)	$ 10.06
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	247,500	171,250
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	755,923
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount (in Dollars)	$ 120,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	85,625	100,625
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value (in Dollars)	$ 274,000	$ 339,000
Employee Benefits and Share-based Compensation (in Dollars)	1,495,000	1,052,000
Share-based Payment Arrangement, Noncash Expense (in Dollars)	$ 273,000	$ 312,000
Shares Issued, Shares, Share-based Payment Arrangement, before Forfeiture	950	1,850
Share-based Payment Arrangement, Option [Member]
Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Employee Benefits and Share-based Compensation (in Dollars)	$ 103,000	$ 110,000
Share-based Payment Arrangement, Noncash Expense (in Dollars)	$ 160,000	$ 144,000
Stock Appreciation Rights (SARs) [Member]
Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	5 years
Stock Appreciation Rights (SARs) [Member] \| Employees and Directors [Member]
Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Total Grants from Inception, Gross	2,445,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	615,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	538,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in Dollars per share)	$ 10.06
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	247,500
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture	58,331
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	189,169
United States Post-Retirement Benefit Plan of US Entity, Defined Benefit [Member]
Employee Benefit Plans (Details) [Line Items]
Stock Issued During Period, Shares, Employee Benefit Plan	41,118	39,403
Stock Issued During Period, Value, Employee Benefit Plan (in Dollars)	$ 419,000	$ 417,000
APIC, Share-based Payment Arrangement, ESPP, Increase for Cost Recognition (in Dollars)	$ 325,000	$ 236,000
Common Stock, Capital Shares Reserved for Future Issuance	498,115	507,204
Income Incentive Pool [Member]
Employee Benefit Plans (Details) [Line Items]
Accrued Bonuses (in Dollars)	$ 550,000	$ 0
Restricted Stock Plan [Member]
Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		0		375,000
Deferred Compensation Agreement [Member]
Employee Benefit Plans (Details) [Line Items]
Deferred Compensation Arrangement with Individual, Description	Under these agreements, each key employee receives specified retirement payments for the remainder of the employee’s life with a minimum payment of ten years’ benefits to either the employee or his or her beneficiaries. The agreements also provide for lump sum payments upon termination of employment without cause and reduced benefits upon early retirement.
Deferred Compensation Arrangement with Individual, Compensation Expense (in Dollars)	$ 1,100,000	$ 640,000