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Note 17 - Regulatory Capital (Details) - Capital Ratios | Dec. 31, 2015 | Dec. 31, 2014
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Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage capital, adequately capitalized, ratio | 4.00% | 4.00%
Tier 1 risk based capital, adequately capitalized, ratio | 6.00% | 4.00%
Common equity tier 1 capital, adequately capitalized, ratio | 4.50% |
Total risk based capital, adequately capitalized, ratio | 8.00% | 8.00%
Adequately capitalized ratio plus capital conservation buffer | 4.00% |
Adequately capitalized ratio plus capital conservation buffer | 8.50% |
Adequately capitalized ratio plus capital conservation buffer | 7.00% |
Adequately capitalized ratio plus capital conservation buffer | 10.50% |
Middlefield Banking Company [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage capital, actual, ratio | 9.23% | 9.25%
Tier 1 risk based capital, actual, ratio | 12.52% | 12.95%
Common equity tier 1 capital, actual, ratio | 12.52% |
Total risk based capital, actual, ratio | 13.73% | 14.19%
Leverage capital, well-capitalized, ratio (bank only) | 5.00% | 5.00%
Tier 1 risk based capital, well-capitalized, ratio (bank only) | 8.00% | 6.00%
Common equity tier 1 capital, well-capitalized, ratio (bank only) | 6.50% |
Total risk based capital, well-capitalized, ratio (bank only) | 10.00% | 10.00%
Middlefield Banc Corp [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage capital, actual, ratio | 8.69% | 9.60%
Tier 1 risk based capital, actual, ratio | 12.00% | 13.38%
Common equity tier 1 capital, actual, ratio | 12.00% |
Total risk based capital, actual, ratio | 13.20% | 14.64%

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