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Note 4 - Securities (Details Textual) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 USD ($) | Jun. 30, 2019 USD ($) | Jun. 30, 2018 USD ($) | Dec. 31, 2018 USD ($)
Debt Securities, Held-to-maturity, Fair Value, Total | $ 119,790,000 |  | $ 119,790,000 |
Debt Securities, Held-to-maturity, Amortized Cost, before Other-than-temporary Impairment | 118,662,000 |  | 118,662,000 |
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, before Tax | $ 1,128,000 |  | $ 1,128,000 |
Number of Temporarily Impaired Securities |  | 171 |  |
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value |  | $ 170,139,000 |  |
Continuous Unrealized Loss Position Aggregate Losses |  | $ 815,000 |  |
Number of Temporarily Impaired Securities Greater than Twelve Months |  | 163 |  |
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value |  | $ 162,263,000 |  | $ 281,626,000
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses |  | 734,000 |  | 7,365,000
National Bank of Blacksburg [Member] | Federal Home Loan Bank of Atlanta [Member] |  |  |  |
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged |  | 530,890,000 |  |
Restricted Stock [Member] |  |  |  |
Restricted Investments |  | $ 1,220,000 |  | 1,220,000
US Government Agencies Debt Securities [Member] |  |  |  |
Number of Temporarily Impaired Securities |  | 162 |  |
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value |  | $ 161,285 |  |
Continuous Unrealized Loss Position Aggregate Losses |  | 733,000 |  |
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value |  | 161,285,000 |  | 259,992,000
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses |  | $ 733,000 |  | 6,450,000
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 |  | $ 978,000 |  |
Continuous Unrealized Loss Position Aggregate Losses |  | 1,000 |  |
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value |  |  |  | 20,758,000
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses |  |  |  | $ 814,000

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- Definition Amount of the collateral pledged in support of federal home loan bank advances outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 + Details
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