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Note 17 - Regulatory Capital - Capital Ratios (Details) | Dec. 31, 2021 | Dec. 31, 2020
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Leverage capital, adequately capitalized, ratio | 0.0400 | 0.0400
Tier 1 risk based capital, adequately capitalized, ratio | 0.0600 | 0.0600
Common equity tier 1 capital, adequately capitalized, ratio | 4.50% | 4.50%
Total risk based capital, adequately capitalized, ratio | 0.0800 | 0.0800
Leverage capital, adequately capitalized plus capital conservation buffer, ratio | 4.00% | 4.00%
Tier 1 risk based capital, adequately capitalized plus capital conservation buffer, ratio | 8.50% | 8.50%
Common equity tier 1 capital, adequately capitalized plus capital conservation buffer, ratio | 7.00% | 7.00%
Total risk based capital, adequately capitalized plus capital conservation buffer, ratio | 10.50% | 10.50%
Middlefield Banking Company [Member] |  |
Leverage capital, actual, ratio | 0.0980 | 0.0945
Tier 1 risk based capital, actual, ratio | 0.1272 | 0.1147
Common equity tier 1 capital, actual, ratio | 12.72% | 11.47%
Total risk based capital, actual, ratio | 0.1397 | 0.1268
Leverage capital, well-capitalized, ratio (bank only) | 0.0500 | 0.0500
Tier 1 risk based capital, well-capitalized, ratio (bank only) | 0.0800 | 0.0800
Common equity tier 1 capital, well-capitalized, ratio (bank only) | 6.50% | 6.50%
Total risk based capital, well-capitalized, ratio (bank only) | 0.1000 | 0.1000
Middlefield Banc Corp [Member] |  |
Leverage capital, actual, ratio | 0.1002 | 0.1022
Tier 1 risk based capital, actual, ratio | 0.1296 | 0.1168
Common equity tier 1 capital, actual, ratio | 12.18% | 10.96%
Total risk based capital, actual, ratio | 0.1421 | 0.1288

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- Definition The minimum common equity tier 1 risk based capital ratio (common equity tier 1 capital divided by risk weighted assets) required for capital adequacy purposes plus capital conservation buffer under the regulatory framework for prompt corrective action. + References No definition available. + Details
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- Definition The common equity tier 1 risk based capital ratio (common equity tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action. + References No definition available. + Details
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- Definition The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes plus capital conservation buffer under the regulatory framework for prompt corrective action. + References No definition available. + Details
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