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Note 7 - Loans and Related Allowance for Loan and Lease Losses (Details) - Impaired Loans by Class (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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With no related allowance recorded: |  |
Recorded investment, with no related allowance | $ 7,909 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment | $ 10,119 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Unpaid principal balance, with no related allowance | 7,891 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance | 10,107 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
With an allowance recorded: |  |
Recorded investment, with related allowance | 4,148 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment | 4,249 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
Unpaid principal balance, with related allowance | 4,142 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance | 4,246 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Related allowance | 998 us-gaap_ImpairedFinancingReceivableRelatedAllowance | 1,596 us-gaap_ImpairedFinancingReceivableRelatedAllowance
Total: |  |
Recorded investment | 12,057 us-gaap_ImpairedFinancingReceivableRecordedInvestment | 14,368 us-gaap_ImpairedFinancingReceivableRecordedInvestment
Unpaid principal balance | 12,033 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance | 14,353 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Related allowance | 998 us-gaap_ImpairedFinancingReceivableRelatedAllowance | 1,596 us-gaap_ImpairedFinancingReceivableRelatedAllowance
Commercial and Industrial [Member] |  |
With no related allowance recorded: |  |
Recorded investment, with no related allowance | 692 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 1,146 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
Unpaid principal balance, with no related allowance | 691 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 1,145 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
With an allowance recorded: |  |
Recorded investment, with related allowance | 369 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 247 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
Unpaid principal balance, with related allowance | 368 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 247 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
Related allowance | 65 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 83 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
Total: |  |
Recorded investment | 1,061 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 1,393 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
Unpaid principal balance | 1,059 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 1,392 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
Related allowance | 65 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember | 83 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialAndIndustrialMember
Real Estate Construction [Member] |  |
With no related allowance recorded: |  |
Recorded investment, with no related allowance | 2,286 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 2,707 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
Unpaid principal balance, with no related allowance | 2,281 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 2,705 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
With an allowance recorded: |  |
Recorded investment, with related allowance | 181 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 589 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
Unpaid principal balance, with related allowance | 181 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 589 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
Related allowance | 181 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 589 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
Total: |  |
Recorded investment | 2,467 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 3,296 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
Unpaid principal balance | 2,462 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 3,294 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
Related allowance | 181 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember | 589 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_RealEstateConstructionMember
Residential Real Estate Mortgage [Member] |  |
With no related allowance recorded: |  |
Recorded investment, with no related allowance | 1,857 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 2,202 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
Unpaid principal balance, with no related allowance | 1,855 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 2,197 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
With an allowance recorded: |  |
Recorded investment, with related allowance | 2,625 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 2,981 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
Unpaid principal balance, with related allowance | 2,622 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 2,978 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
Related allowance | 550 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 892 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
Total: |  |
Recorded investment | 4,482 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 5,183 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
Unpaid principal balance | 4,477 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 5,175 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
Related allowance | 550 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember | 892 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ResidentialRealEstateMortgageMember
Commercial Real Estate Mortgage [Member] |  |
With no related allowance recorded: |  |
Recorded investment, with no related allowance | 3,074 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 4,064 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
Unpaid principal balance, with no related allowance | 3,064 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 4,060 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
With an allowance recorded: |  |
Recorded investment, with related allowance | 967 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 426 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
Unpaid principal balance, with related allowance | 965 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 426 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
Related allowance | 200 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 30 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
Total: |  |
Recorded investment | 4,041 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 4,490 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
Unpaid principal balance | 4,029 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 4,486 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
Related allowance | 200 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember | 30 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_CommercialRealEstateMortgageMember
Consumer Installment [Member] |  |
With an allowance recorded: |  |
Recorded investment, with related allowance | 6 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember | 6 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember
Unpaid principal balance, with related allowance | 6 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember | 6 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember
Related allowance | 2 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember | 2 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember
Total: |  |
Recorded investment | 6 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember | 6 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember
Unpaid principal balance | 6 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember | 6 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember
Related allowance | $ 2 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember | $ 2 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = mbcn_ConsumerInstallmentMember

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- Definition Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953550-111524 + Details
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- Definition Amount of allowance for credit losses related to recorded investment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524 + Details
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- Definition Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524 + Details
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