Note 12 - Minimum Regulatory Capital Requirement (Details) - Minimum Capital Requirements (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
NBI Consolidated [Member]
Total capital (to risk weighted assets)
Total capital (to risk weighted assets) actual amount	$ 172,976	$ 162,763
Total capital (to risk weighted assets) actual ratio	24.90%	23.60%
Total capital (to risk weighted assets) minimum capital requirement amount	55,615	55,192
Total capital (to risk weighted assets) minimum capital requirement ratio	8.00%	8.00%
Tier 1 capital (to risk weighted assets)
Tier 1 capital (to risk weighted assets) actual amount	164,713	154,536
Tier 1 capital (to risk weighted assets) actual ratio	23.70%	22.40%
Tier 1 capital (to risk weighted assets) minimum capital requirement amount	27,807	27,596
Tier 1 capital (to risk weighted assets) minimum capital requirement ratio	4.00%	4.00%
Tier 1 capital (to average assets)
Tier 1 capital (to average assets) actual amount	164,713	154,536
Tier 1 capital (to average assets) actual ratio	14.60%	14.10%
Tier 1 capital (to average assets) minimum capital requirement amount	45,122	43,946
Tier 1 capital (to average assets) minimum capital requirement ratio	4.00%	4.00%
National Bank of Blacksburg [Member]
Total capital (to risk weighted assets)
Total capital (to risk weighted assets) actual amount	170,665	160,049
Total capital (to risk weighted assets) actual ratio	24.60%	23.30%
Total capital (to risk weighted assets) minimum capital requirement amount	55,438	54,980
Total capital (to risk weighted assets) minimum capital requirement ratio	8.00%	8.00%
Total capital (to risk weighted assets) minimum to be well capitalized under prompt corrective action provisions amount	69,298	68,726
Total capital (to risk weighted assets) minimum to be well capitalized under prompt corrective action provisions ratio	10.00%	10.00%
Tier 1 capital (to risk weighted assets)
Tier 1 capital (to risk weighted assets) actual amount	162,402	151,822
Tier 1 capital (to risk weighted assets) actual ratio	23.40%	22.10%
Tier 1 capital (to risk weighted assets) minimum capital requirement amount	27,719	27,490
Tier 1 capital (to risk weighted assets) minimum capital requirement ratio	4.00%	4.00%
Tier 1 capital (to risk weighted assets) minimum to be well capitalized under prompt corrective action provisions amount	41,579	41,235
Tier 1 capital (to risk weighted assets) minimum to be well capitalized under prompt corrective action provisions ratio	6.00%	6.00%
Tier 1 capital (to average assets)
Tier 1 capital (to average assets) actual amount	162,402	151,822
Tier 1 capital (to average assets) actual ratio	14.40%	13.80%
Tier 1 capital (to average assets) minimum capital requirement amount	45,074	43,904
Tier 1 capital (to average assets) minimum capital requirement ratio	4.00%	4.00%
Tier 1 capital (to average assets) minimum to be well capitalized under prompt corrective action provisions amount	$ 56,342	$ 54,880
Tier 1 capital (to average assets) minimum to be well capitalized under prompt corrective action provisions ratio	5.00%	5.00%

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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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