XML 61 R51.htm IDEA: XBRL DOCUMENT v3.25.3

Note 3 - Loans and Allowance for Credit Losses - Amortized Cost of Modified Loans (Details) $ in Thousands	Sep. 30, 2025 USD ($)
Modified, past 12 months	$ 9,970
Financial Asset, Not Past Due [Member]
Modified, past 12 months	9,970
Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member]
Modified, past 12 months	9,970
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	9,970
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Modified, past 12 months	9,970
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	9,970
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | Other Consumer Loans [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | Other Consumer Loans [Member] | Financial Asset, Not Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | Other Consumer Loans [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Modified, past 12 months	0
Retail Portfolio Segment [Member] | Other Consumer Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Modified, past 12 months	$ 0

X

- 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://fasb.org/us-gaap/role/ref/otherTransitionRef
-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/otherTransitionRef
-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

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

X

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetNotPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=mbwm_FinancialAsset30To89DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_CommercialAndIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_RealEstateOwnerOccupiedLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_RealEstateNonOwnerOccupiedLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_OneToFourFamilyMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_OtherConsumerLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: