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Note 17 - Regulatory Capital - Capital Ratios (Details) | Dec. 31, 2024 | Dec. 31, 2023
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Leverage capital, adequately capitalized, ratio | 0.04 | 0.04
Tier 1 risk based capital, adequately capitalized, ratio | 0.06 | 0.06
Common equity tier 1 capital, adequately capitalized, ratio | 4.50% | 4.50%
Total risk based capital, adequately capitalized, ratio | 0.08 | 0.08
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 | 0.107 | 0.1048
Tier 1 risk based capital, actual, ratio | 0.1199 | 0.1182
Common equity tier 1 capital, actual, ratio | 11.99% | 11.82%
Total risk based capital, actual, ratio | 0.1324 | 0.1308
Leverage capital, well-capitalized, ratio (bank only) | 0.05 | 0.05
Tier 1 risk based capital, well-capitalized, ratio (bank only) | 0.08 | 0.08
Common equity tier 1 capital, well-capitalized, ratio (bank only) | 6.50% | 6.50%
Total risk based capital, well-capitalized, ratio (bank only) | 0.10 | 0.10
Middlefield Banc Corp [Member] |  |
Leverage capital, actual, ratio | 0.1086 | 0.1068
Tier 1 risk based capital, actual, ratio | 0.1228 | 0.1218
Common equity tier 1 capital, actual, ratio | 11.78% | 11.66%
Total risk based capital, actual, ratio | 0.1354 | 0.1343

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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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