Number of financing receivables that have been modified by troubled debt restructurings.

No definition available.

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Namespace Prefix:	mbcn_
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Balance Type:	na
Period Type:	duration

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

No definition available.

+ Details

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Namespace Prefix:	mbcn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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- Definition

Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-33

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Accumulated amortized cost of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-42

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-33

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 310
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481746/310-40-50-4

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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Balance Type:
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- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
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Data Type:	na
Balance Type:
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- Details

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Data Type:	na
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- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Data Type:	na
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- Details

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- Details

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- Details

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Note 8 - Loans and Related Allowance for Credit Losses - Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Modified, Amortized cost	$ 4,336		$ 3,300
to Total Financing Receivables, Percentage	0.31%
Commercial And Industrial [Member]
Modified, Amortized cost	$ 149
to Total Financing Receivables, Percentage	0.01%
Number of contracts		1
Pre-modification outstanding recorded investment		$ 25
Post-modification outstanding recorded investment		$ 25
Commercial Real Estate Portfolio Segment [Member] \| Non-owner occupied Loan [Member]
Modified, Amortized cost	$ 4,179
to Total Financing Receivables, Percentage	0.30%
Consumer Portfolio Segment [Member]
Modified, Amortized cost	$ 8
to Total Financing Receivables, Percentage	0.00%
Extended Maturity [Member]
Modified, Amortized cost	$ 4,336
Extended Maturity [Member] \| Commercial And Industrial [Member]
Modified, Amortized cost	149
Number of contracts		1
Extended Maturity [Member] \| Commercial Real Estate Portfolio Segment [Member] \| Non-owner occupied Loan [Member]
Modified, Amortized cost	4,179
Extended Maturity [Member] \| Consumer Portfolio Segment [Member]
Modified, Amortized cost	8
Other Restructurings [Member] \| Commercial And Industrial [Member]
Number of contracts		0
Payment Deferral [Member]
Modified, Amortized cost	0
Payment Deferral [Member] \| Commercial And Industrial [Member]
Modified, Amortized cost	0
Payment Deferral [Member] \| Commercial Real Estate Portfolio Segment [Member] \| Non-owner occupied Loan [Member]
Modified, Amortized cost	0
Payment Deferral [Member] \| Consumer Portfolio Segment [Member]
Modified, Amortized cost	0
Payment Deferral and Extended Maturity [Member]
Modified, Amortized cost	0
Payment Deferral and Extended Maturity [Member] \| Commercial And Industrial [Member]
Modified, Amortized cost	0
Payment Deferral and Extended Maturity [Member] \| Commercial Real Estate Portfolio Segment [Member] \| Non-owner occupied Loan [Member]
Modified, Amortized cost	0
Payment Deferral and Extended Maturity [Member] \| Consumer Portfolio Segment [Member]
Modified, Amortized cost	0
Interest Rate Reduction and Term Past Due [Member]
Modified, Amortized cost	0
Interest Rate Reduction and Term Past Due [Member] \| Commercial And Industrial [Member]
Modified, Amortized cost	0
Interest Rate Reduction and Term Past Due [Member] \| Commercial Real Estate Portfolio Segment [Member] \| Non-owner occupied Loan [Member]
Modified, Amortized cost	0
Interest Rate Reduction and Term Past Due [Member] \| Consumer Portfolio Segment [Member]
Modified, Amortized cost	$ 0