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Note 15 - Regulatory Restrictions (Details) (USD $) In Millions, except Share data, unless otherwise specified | 1 Months Ended | 63 Months Ended |  |
--- | --- | --- | --- | ---
Apr. 30, 2012 | Dec. 31, 2014 | Dec. 31, 2013 | Jan. 14, 2013
Note 15 - Regulatory Restrictions (Details) [Line Items] |  |  |  |
Reserves Required by Federal Reserve Bank |  | $ 6.8 mbcn_ReservesRequiredByFederalReserveBank | $ 7.4 mbcn_ReservesRequiredByFederalReserveBank |
Percent of Common Stock |  |  | 10.00%mbcn_PercentOfCommonStock |
Pursuant to Regulatory Clearance [Member] | One Investor [Member] |  |  |  |
Note 15 - Regulatory Restrictions (Details) [Line Items] |  |  |  |
Maximum Ownership of Stock |  |  |  | 24.99%mbcn_MaximumOwnershipOfStock / us-gaap_CounterpartyNameAxis = mbcn_OneInvestorMember / us-gaap_StatementScenarioAxis = mbcn_PursuantToRegulatoryClearanceMember
One Investor [Member] |  |  |  |
Note 15 - Regulatory Restrictions (Details) [Line Items] |  |  |  |
Stock Issued During Period, Shares, New Issues | 196,635 us-gaap_StockIssuedDuringPeriodSharesNewIssues / us-gaap_CounterpartyNameAxis = mbcn_OneInvestorMember |  |  |
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners | 9.90%us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners / us-gaap_CounterpartyNameAxis = mbcn_OneInvestorMember |  |  |
Maximum Ownership of Stock |  | 10.00%mbcn_MaximumOwnershipOfStock / us-gaap_CounterpartyNameAxis = mbcn_OneInvestorMember |  |
Emerald Bank [Member] |  |  |  |
Note 15 - Regulatory Restrictions (Details) [Line Items] |  |  |  |
Nonperforming Assets Sold |  | 5.8 mbcn_NonperformingAssetsSold / dei_LegalEntityAxis = mbcn_EmeraldBankMember |  |
Middlefield Banking Company [Member] |  |  |  |
Note 15 - Regulatory Restrictions (Details) [Line Items] |  |  |  |
Amount Available for Payment of Dividends |  |  | $ 10.2 mbcn_AmountAvailableForPaymentOfDividends / dei_LegalEntityAxis = mbcn_MiddlefieldBankingCompanyMember |

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X
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Period Type: | instant

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Period Type: | duration

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- Definition Reserves required by Federal Reserve Bank. + References No definition available. + Details
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- Definition Number of new stock issued during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 + Details
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- Details
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- Details
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Period Type: |

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- Details
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- Details
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Period Type: |