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Note 1 - Summary of Significant Accounting Policies (Details Textual) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2020 USD ($) shares | Jun. 30, 2019 USD ($) shares | Jun. 30, 2020 USD ($) shares | Jun. 30, 2019 USD ($) shares | Dec. 31, 2019 USD ($)
Participating Interest In Loans, Losses or Charge-offs |  |  |  | $ 0 |  |
Stock Issued During Period, Value, New Issues |  | $ 55,000 | $ 12,000 | $ 161,000 | $ 59,000 |
Common Stock Including Additional Paid in Capital [Member] |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues (in shares) | shares |  | 5,466 | 3,253 | 9,122 | 5,257 |
Stock Issued During Period, Value, New Issues |  | $ 55,000 | $ 12,000 | $ 161,000 | $ 59,000 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares) | shares | [1] | 6,241 | 3,390 | 7,030 | 3,390 |
Stock Issued During Period, Shares, Restricted Stock Award, Gross (in shares) | shares |  |  | 6,764 | 365 | 7,787 |
Directors' Stock Purchase Plan [Member] |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues (in shares) | shares |  |  |  | 6,658 |  |
Stock Issued During Period, Value, New Issues |  |  |  | $ 186,000 |  |
Employee Stock Purchase Plan [Member] |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues (in shares) | shares |  |  |  | 2,464 |  |
Stock Issued During Period, Value, New Issues |  |  |  | $ 60,000 |  |
Credit Concentration Risk [Member] | Participating Interests in Mortgage Loans [Member] |  |  |  |  |  |
Number Of Mortgage Bankers |  | 15 |  | 15 |  |
Concentration Risk, Percentage |  |  |  | 12.00% |  |
Number of Participating Interest In Loans To Other Financial Institutions Over 30 Days |  | 17 |  | 17 |  | 26
Number of Participating Interest In Loans To Other Financial Institutions |  | 340 |  | 340 |  | 222
Participating Interest In Loans To Other Financial Institutions Over 30 Days |  | $ 4,600,000 |  | $ 4,600,000 |  | $ 6,400,000
[1] | The amount shown represents the number of shares issued in cashless transactions where some taxes are netted on a portion of the exercises.

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