XML 76 R72.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 4 - Loans and Allowance for Loan Losses (Details) - Nonperforming Loans (USD $)
Dec. 31, 2014
Dec. 31, 2013
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 $ 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 $ 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		 0us-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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonaccrual loans 26,048,000us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 6,718,000us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonperforming loans 26,048,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 6,718,000mbwm_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 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		 0us-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 0us-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 0us-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 0us-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 0us-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 0us-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 0us-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 26,000us-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 0us-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 26,000us-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 26,000us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		   
Nonaccrual loans 3,358,000us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		   
Nonperforming loans 3,384,000mbwm_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 26,000us-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 6,478,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 1,501,000mbwm_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 209,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 785,000mbwm_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 18,062,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 389,000mbwm_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 378,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 168,000mbwm_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 106,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 208,000mbwm_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 25,233,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 3,051,000mbwm_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 800,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 788,000mbwm_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 3,399,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 2,879,000mbwm_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 4,199,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 3,667,000mbwm_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 $ 29,432,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 $ 6,718,000mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoans
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember