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Short-term Borrowings (Details) - Repurchase Agreements (Detail) - Overnight and Continuous [Member] - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
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Repurchase agreements: |  |
Repurchase agreements | $ 2,929 | $ 3,181
US Government Agencies Debt Securities [Member] |  |
Repurchase agreements: |  |
Repurchase agreements | 1,052 | 1,090
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] |  |
Repurchase agreements: |  |
Repurchase agreements | $ 1,877 | $ 2,091

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- Definition Repurchase Agreements Abstract 0 + References No definition available. + Details
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Namespace Prefix: | mbcn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Carrying amount of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
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- Details
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Data Type: | na
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |