XML 74 R51.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due (USD $)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Commercial and Industrial [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
Recorded principal balance $ 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 $ 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
Commercial and Industrial [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Vacant Land and Land Development and Residential Construction Loan [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Vacant Land and Land Development and Residential Construction Loan [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Real Estate Owner Occupied Loan [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateOwnerOccupiedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateOwnerOccupiedLoanMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateOwnerOccupiedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateOwnerOccupiedLoanMember
Real Estate Owner Occupied Loan [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateOwnerOccupiedLoanMember		  
Recorded principal balance 1,339,000us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateOwnerOccupiedLoanMember		  
Real Estate Non Owner Occupied Loan [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateNonOwnerOccupiedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateNonOwnerOccupiedLoanMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateNonOwnerOccupiedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateNonOwnerOccupiedLoanMember
Real Estate Non Owner Occupied Loan [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateNonOwnerOccupiedLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateNonOwnerOccupiedLoanMember		  
Real Estate Multi Family and Residential Rental Loan [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember
Real Estate Multi Family and Residential Rental Loan [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		  
Recorded principal balance 1,339,000us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		  
Real Estate Multi Family and Residential Rental Loan [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember
Real Estate Multi Family and Residential Rental Loan [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember		  
Home Equity and Other [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_HomeEquityAndOtherMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_HomeEquityAndOtherMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_HomeEquityAndOtherMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_HomeEquityAndOtherMember
Home Equity and Other [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_HomeEquityAndOtherMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_HomeEquityAndOtherMember		  
1-4 Family Mortgages [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_OneToFourFamilyMortgagesMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_OneToFourFamilyMortgagesMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_OneToFourFamilyMortgagesMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_OneToFourFamilyMortgagesMember
1-4 Family Mortgages [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_OneToFourFamilyMortgagesMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_OneToFourFamilyMortgagesMember		  
Retail Loan [Member] | Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= mbwm_RetailLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= mbwm_RetailLoanMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= mbwm_RetailLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= mbwm_RetailLoanMember
Retail Loan [Member] | Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= mbwm_RetailLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivablePortfolioSegmentAxis
= mbwm_RetailLoanMember		  
Originated Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
Acquired Loan [Member]    
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings within the Previous Twelve Months That Became Over 30 Days Past Due [Line Items]    
Number of contracts 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		  
Recorded principal balance $ 1,339,000us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember