Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
Apr. 30, 2021	Apr. 30, 2020
Income Tax Contingency [Line Items]
Additional valuation allowance deferred income tax assets	$ 79,000
Effective income tax rate, provisions (benefit)	23.40%	29.40%
Gross tax-effected unrecognized tax benefits	$ 0	$ 0
Federal
Income Tax Contingency [Line Items]
Net operating loss carryforwards	0
State
Income Tax Contingency [Line Items]
Net operating loss carryforwards	17,700,000	17,700,000
Tax credit carryforwards	2,900,000	2,900,000
Valuation allowances for net operating loss carryforward	904,000	904,000
Valuation allowances for tax credits	$ 2,300,000	$ 2,300,000
State \| Minimum
Income Tax Contingency [Line Items]
Operating loss carry forwards expiration dates	Apr. 30, 2027
State tax credit carryforwards expire date	Apr. 30, 2023
State \| Maximum
Income Tax Contingency [Line Items]
Operating loss carry forwards expiration dates	Apr. 30, 2040
State tax credit carryforwards expire date	Apr. 30, 2025

Tax cuts and jobs act change in tax rate provisional income Tax expense (benefit).

No definition available.

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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Expiration date of each operating loss carryforward included in operating loss carryforward, in CCYY-MM-DD format.

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The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

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- Definition

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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Expiration date of the tax credit carryforward, in CCYY-MM-DD format.

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Amount of valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from tax credit carryforwards for which it is more likely than not that a tax benefit will not be realized.

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Amount of unrecognized tax benefits.

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