Note 10 - Stock-based Compensation Expense - Changes in Restricted Stock Units (Details) - $ / shares	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Vested (in shares)	(258,000)
Restricted Stock Units (RSUs) [Member]
Outstanding (in shares)	13,000	3,000
Outstanding, grant date weighted average fair value (in dollars per share)	$ 1.97	$ 3.03
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	165,000	144,000
Granted, grant date weighted average fair value (in dollars per share)	$ 2.61	$ 1.96
Vested (in shares)	(168,000)	(134,000)
Vested, grant date weighted average fair value (in dollars per share)	$ 2.57	$ 1.98
Outstanding (in shares)	10,000	13,000
Outstanding, grant date weighted average fair value (in dollars per share)	$ 2.57	$ 1.97

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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- Definition

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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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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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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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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