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Note 17 - Regulatory Capital | 12 Months Ended
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Dec. 31, 2017
Notes to Financial Statements |
Regulatory Capital Requirements under Banking Regulations [Text Block] |
17. | REGULATORY CAPITAL
The Bank and Company are subject to regulatory capital requirements administered by banking agencies. Capital adequacy guidelines and prompt corrective-action regulations involve quantitative measures of assets, liabilities, and certain off-balance-sheet items calculated under regulatory accounting practices. Capital amounts and classifications are also subject to qualitative judgments by regulators about components, risk weightings, and other factors and the regulators can lower classifications in certain cases. Failure to meet various capital requirements can initiate regulatory action that could have a direct material effect on the financial stateme nts. As of December 31, 2017, the Bank and Company have met all capital adequacy requirements to which they are subject. The prompt corrective action regulations provide five classifications, including well capitalized, adequately capitalized, under-capitalized, significantly undercapitalized, and critically undercapitalized, although these terms are not used to represent overall financial condition. If an institution is adequately capitalized, regulatory approval is required before the institution may accept brokered deposits. If an institution is undercapitalized, capital distributions are limited, as is asset growth and expansion, and plans for capital restoration are required. The Basel III Capital Rules became effective for the Bank on January 1, 2015 and certain provisions are subject to a phase-in period. The implementation of the capital conservation buffer began January 1, 2016 at the 0.625% level and will be phased in over a four -year period (increasing by that amount on each subsequent January 1, until it reaches 2.5% on January 1, 2019). The capital conservation buffer is designed to absorb losses during periods of economic stress. Banking institutions with a ratio of Common Equity Tier 1 capital to risk-weighted assets above the minimum but below the conservation buffer (or below the combined capital conservation buffer and countercyclical capital buffer, when the latter is applied) will face constraints on dividends, equity repurchases and compensation based on the amount of the shortfall. The following tables present actual and required capital ratios as of December 31, 2017 and 2016, under the Basel III Capital Rules. Capital levels required to be considered well capitalized are based upon prompt corrective action regulations, as amended to reflect the changes under the Basel III Capital Rules.
|  | As of December 31, 2017 |
|  |  |  |  |  | Tier 1 Risk |  |  | Common |  |  | Total Risk |
|  | Leverage |  |  | Based |  |  | Equity Tier 1 |  |  | Based |
The Middlefield Banking Company |  |  | 9.47 | % |  |  | 10.88 | % |  |  | 10.88 | % |  |  | 11.64 | %
Middlefield Banc Corp. |  |  | 10.20 | % |  |  | 11.64 | % |  |  | 10.79 | % |  |  | 12.41 | %
Adequately capitalized ratio |  |  | 4.00 | % |  |  | 6.00 | % |  |  | 4.50 | % |  |  | 8.00 | %
Adequately capitalized ratio plus fully phased-in capital conservation buffer |  |  | 4.00 | % |  |  | 8.50 | % |  |  | 7.00 | % |  |  | 10.50 | %
Well-capitalized ratio (Bank only) |  |  | 5.00 | % |  |  | 8.00 | % |  |  | 6.50 | % |  |  | 10.00 | %
|  | As of December 31, 2016 |
|  |  |  |  |  | Tier 1 Risk |  |  | Common |  |  | Total Risk |
|  | Leverage |  |  | Based |  |  | Equity Tier 1 |  |  | Based |
The Middlefield Banking Company |  |  | 9.29 | % |  |  | 13.03 | % |  |  | 13.03 | % |  |  | 14.25 | %
Middlefield Banc Corp. |  |  | 9.27 | % |  |  | 13.07 | % |  |  | 13.07 | % |  |  | 15.75 | %
Adequately capitalized ratio |  |  | 4.00 | % |  |  | 6.00 | % |  |  | 4.50 | % |  |  | 8.00 | %
Adequately capitalized ratio plus fully phased-in capital conservation buffer |  |  | 4.00 | % |  |  | 8.50 | % |  |  | 7.00 | % |  |  | 10.50 | %
Well-capitalized ratio (Bank only) |  |  | 5.00 | % |  |  | 8.00 | % |  |  | 6.50 | % |  |  | 10.00 | %

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- Definition The entire disclosure for banks, savings institutions, and credit unions, for regulatory capital requirements imposed by the Federal Reserve System (FRB), the Federal Deposit Insurance Corporation (FDIC), the Office of Thrift Supervision (OTS) or for any state imposed capital requirements, as applicable. The disclosure may include (1) a description of regulatory capital requirements (a) for capital adequacy purposes and (b) established by the prompt corrective action provisions of Section 38 of the Federal Depository Insurance Act; (2) the actual or possible material effects of noncompliance with such requirements; (3) whether the entity is in compliance with the regulatory capital requirements including (a) required and actual ratios and amounts of Tier 1 leverage, Tier 1 risk-based, and total risk-based capital, tangible capital (for savings institutions), and Tier 3 capital for market risk (for certain banks and bank holding companies), (b) factors that may significantly affect capital adequacy; (4) the prompt corrective action category in which the entity was classified as of its most recent notification; (5) whether management believes any conditions or events since notification have changed the entity's category. Also may include additional information that might be disclosed in situations where substantial doubt about the entity's ability to continue as a going concern for a reasonable period of time. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1G -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958577-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1C -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958572-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1E -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958574-112826 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958569-112826 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1F -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958575-112826 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1D -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958573-112826 + Details
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