Note 14 - Stock Compensation Plans (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			176,866
Stock Issued During Period, Shares, Restricted Stock Award, Gross	17,950	14,750
Stock Issued During Period, Value, Restricted Stock Award, Gross	$ 558,000	$ 456,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 31.10	$ 30.90
Share Based Compensation Arrangement By Share Based Payment Award Vested, Percentage	100.00%
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0
Share-based Payment Arrangement, Expense	$ 368,000	$ 269,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 951,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	19,833
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 31.10
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

The percentage of options and restricted stock awards that are vested.

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

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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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Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards.

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Aggregate value of stock related to Restricted Stock Awards issued during the period.

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