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Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans (USD $) | Dec. 31, 2014 | Dec. 31, 2013
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Originated Loan [Member] | Commercial and Industrial [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | $ 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | $ 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember
Originated Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Originated Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember
Originated Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
Originated Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
Originated Loan [Member] | Commercial Portfolio Segment [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember
Originated Loan [Member] | Retail Home Equity and Other [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailHomeEquityAndOtherMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailHomeEquityAndOtherMember
Originated Loan [Member] | Retail 1-4 Family Mortgages [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_Retail1To4FamilyMortgagesMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_Retail1To4FamilyMortgagesMember
Originated Loan [Member] | Retail Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember
Originated Loan [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Nonaccrual loans | 26,048,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 6,718,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Nonperforming loans | 26,048,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 6,718,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Originated Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember
Acquired Loan [Member] | Commercial and Industrial [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Acquired Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Acquired Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember |
Acquired Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember |
Acquired Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember |
Acquired Loan [Member] | Commercial Portfolio Segment [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember |
Acquired Loan [Member] | Retail Home Equity and Other [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 26,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailHomeEquityAndOtherMember |
Acquired Loan [Member] | Retail 1-4 Family Mortgages [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_Retail1To4FamilyMortgagesMember |
Acquired Loan [Member] | Retail Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 26,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |
Acquired Loan [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 26,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember |
Nonaccrual loans | 3,358,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember |
Nonperforming loans | 3,384,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember |
Acquired Loan [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Loans past due 90 days or more still accruing interest | 26,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |
Commercial and Industrial [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 6,478,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 1,501,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 209,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 785,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Commercial Real Estate Owner Occupied Loan [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 18,062,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 389,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Commercial Real Estate Non Owner Occupied Loan [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 378,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 168,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 106,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 208,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Commercial Portfolio Segment [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 25,233,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 3,051,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Retail Home Equity and Other [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 800,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailHomeEquityAndOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 788,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailHomeEquityAndOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Retail 1-4 Family Mortgages [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 3,399,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_Retail1To4FamilyMortgagesMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 2,879,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_Retail1To4FamilyMortgagesMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Retail Loan [Member] | Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | 4,199,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 3,667,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Nonperforming Financing Receivable [Member] |  |
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans [Line Items] |  |
Nonperforming loans | $ 29,432,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | $ 6,718,000 mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember

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- Definition Financing receivables past due 90 days or more and still accruing interest and nonaccrual loans + References No definition available. + Details
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- Definition Recorded investment in financing receivables that are 90 days or more past due and still accruing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524 + Details
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- Definition Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524 + Details
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