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Note 3 - Securities (Details Textual) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Number of Temporarily Impaired Securities | 62 |  |
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value | $ 74,662 |  |
Continuous Unrealized Loss Position Aggregate Losses | $ 503 |  |
Number of Temporarily Impaired Securities Greater than Twelve Months | 2 |  |
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value | $ 4,695 | $ 39,553 |
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses | 5 | 85 |
Debt Securities, Available-for-sale, Restricted | 251,048 | 220,999 |
Available-for-sale Securities, Gross Realized Gains | 108 | 566 | $ 17
Debt Securities, Held-to-maturity, Fair Value, Total |  |  | 119,790
Debt Securities, Held-to-maturity, Amortized Cost, before Other-than-temporary Impairment |  |  | 118,662
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, before Tax |  |  | 1,128
National Bank of Blacksburg [Member] | Federal Home Loan Bank of Atlanta [Member] |  |  |
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged | 558,703 |  |
Restricted Stock [Member] |  |  |
Restricted Investments | $ 1,279 | 1,220 |
US States and Political Subdivisions Debt Securities [Member] |  |  |
Number of Temporarily Impaired Securities | 1 |  |
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value | $ 635 |  |
Continuous Unrealized Loss Position Aggregate Losses | 3 |  |
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value | 635 | 591 |
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses | $ 3 | 48 |
Collateralized Mortgage Backed Securities [Member] |  |  |
Number of Temporarily Impaired Securities | 1 |  |
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value | $ 4,060 |  |
Continuous Unrealized Loss Position Aggregate Losses | 2 |  |
Securities Sold [Member] |  |  |
Available-for-sale Securities, Gross Realized Gains | 43 | 438 | 1
Securities Called [Member] |  |  |
Available-for-sale Securities, Gross Realized Gains | $ 65 | $ 128 | $ 16

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