Note 8 - Stock-based Compensation (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Share-Based Payment Arrangement, Expense	$ 135,000	$ 97,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross	244,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 9.33
Share-Based Payment Arrangement, Option [Member]
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
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 3,200,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	3 years 2 months 12 days
Share-Based Payment Arrangement, Option [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage	25.00%
Director [Member]
Share-based Payment Arrangement, Annual Equity Reatiner	$ 40,000
Director [Member] \| Restricted Stock [Member]
Share-Based Payment Arrangement, Expense	$ 40,000	$ 40,000

Amount of annual equity retainer under share-based payment arrangement.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Percentage of vesting of award under share-based payment arrangement.

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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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