Note 6 - Stock Compensation Plan (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Apr. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			176,866
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	0
Share-based Payment Arrangement, Expense	$ 90,000	$ 75,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 694,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	3 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	37,783
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	88,433
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	10 years

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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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Number of options outstanding, including both vested and non-vested options.

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Expected term of 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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