XML 54 R42.htm IDEA: XBRL DOCUMENT
v3.22.2

Note 7 - Investment and Equity Securities - Amortized Cost and Fair Values of Securities Available for Sale (Details) - USD ($) $ in Thousands | Jun. 30, 2022 | Mar. 31, 2022 | Dec. 31, 2021
--- | --- | --- | ---
Amortized cost | $ 194,226 | $ 194,226 | $ 165,817
Gross unrealized gains |  | 140 | 4,922
Gross unrealized losses |  | (22,408) | (540)
Investment securities available for sale, at fair value | $ 171,958 | 171,958 | 170,199
Subordinated Debt Securities [Member] |  |  |
Amortized cost |  | 32,300 | 32,300
Gross unrealized gains |  | 32 | 356
Gross unrealized losses |  | (1,024) | (119)
Investment securities available for sale, at fair value |  | 31,308 | 32,537
Taxable Municipal Bonds [Member] |  |  |
Amortized cost |  | 500 | 500
Gross unrealized gains |  | 1 | 2
Gross unrealized losses |  | 0 | 0
Investment securities available for sale, at fair value |  | 501 | 502
Nontaxable Municipal Bonds [Member] |  |  |
Amortized cost |  | 152,436 | 122,877
Gross unrealized gains |  | 105 | 4,307
Gross unrealized losses |  | (20,734) | (341)
Investment securities available for sale, at fair value |  | 131,807 | 126,843
Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member] |  |  |
Amortized cost |  | 8,990 | 10,140
Gross unrealized gains |  | 2 | 257
Gross unrealized losses |  | (650) | (80)
Investment securities available for sale, at fair value |  | $ 8,342 | $ 10,317

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbcn_SubordinatedDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_TaxableMunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_NontaxableMunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |