Note 2 - Stock-based Compensation - Unvested Restricted Stock and Deferred Stock (Details) - Employee Deferred Stock Award [Member] - $ / shares	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Non-Vested Balance (in shares)	43,400
Non-Vested Balance, weighted average fair value per share (in dollars per share)	$ 12.48
Granted (in shares)	18,600	27,900
Granted, weighted average fair value per share (in dollars per share)	$ 21.62	$ 13.33
Vested (in shares)	(20,800)
Vested, weighted average fair value per share (in dollars per share)	$ 21.32
Forfeited (in shares)	0
Forfeited, weighted average fair value per share (in dollars per share)	$ 0
Non-Vested Balance (in shares)	41,200
Non-Vested Balance, weighted average fair value per share (in dollars per share)	$ 16.62

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
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-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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