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Note 3 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Restructurings By Class (Details) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 USD ($) | Mar. 31, 2017
Number of contracts | 2 | 0
Pre-modification outstanding principal balance | $ 2,882 |
Post-modification outstanding principal balance | $ 2,882 |
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member] |  |
Number of contracts | 2 |
Pre-modification outstanding principal balance | $ 2,882 |
Post-modification outstanding principal balance | $ 2,882 |

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