The amount of payment deferral requests received on financing receivable.

No definition available.

Name:	mbcn_FinancingReceivableAmountOfPaymentDeferralRequestsReceived
Namespace Prefix:	mbcn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The number of payment deferral requests received on financing receivable.

No definition available.

Name:	mbcn_FinancingReceivableNumberOfPaymentDeferralRequestsReceived
Namespace Prefix:	mbcn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of principal and interest payments and extension of maturity date payment deferrals on financing receivable.

No definition available.

Name:	mbcn_FinancingReceivableNumberOfPrincipalAndInterestAndExtensionOfMaturityDatePaymentDeferrals
Namespace Prefix:	mbcn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The amount of principal and interest payment and extension of maturity date payment deferrals on financing receivable.

No definition available.

Name:	mbcn_FinancingReceivablePrincipalAndInterestPaymentsAndExtensionOfMaturityDatePaymentDeferrals
Namespace Prefix:	mbcn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of loans to be funded under the Payment Protection Plan.

No definition available.

Name:	mbcn_PaymentProtectionPlanAmountToBeFunded
Namespace Prefix:	mbcn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The number of loan applications approved under the Payroll Protection Plan.

No definition available.

Name:	mbcn_PayrollProtectionPlanNumberOfLoanApplicationsApproved
Namespace Prefix:	mbcn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=mbcn_ResidentialMortgageAndConsumerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 10 - Risks and Uncertainties (Details Textual) - Subsequent Event [Member] $ in Millions	May 03, 2020 USD ($)	May 01, 2020 USD ($)	Apr. 21, 2020 USD ($)
Payroll Protection Plan, Number of Loan Applications Approved	1,048
Payment Protection Plan, Amount to be Funded	$ 138.1
Financing Receivable, Number of Payment Deferrals		606
Financing Receivable, Deferred Payments		$ 333.2
Financing Receivable, Number of Principal and Interest Payments and Extension of Maturity Date Payment Deferrals			252
Financing Receivable, Principal and Interest Payments and Extension of Maturity Date Payment Deferrals			$ 147.0
Residential Mortgage and Consumer [Member]
Financing Receivable, Number of Payment Deferrals		59
Financing Receivable, Deferred Payments		$ 7.8