Note 5 - Stock-based Compensation - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
General and administrative expense	$ 484	$ 452	$ 1,469	$ 979
General and Administrative Expense [Member]
General and administrative expense	$ 484	$ 452	$ 1,469	$ 979

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

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-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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