XML 32 R79.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 $)
 12 Months Ended 7 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		  
Recorded principal balance $ 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		 $ 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember
Commercial 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Commercial 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Commercial 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 65,000us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Commercial 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     0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
Commercial 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Commercial 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
Commercial 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Commercial 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
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_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		 65,000us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		  
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     0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember
Retail 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Retail 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember
Retail 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Retail 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember
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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= 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_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember
Recorded principal balance     0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= 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		 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		  
Recorded principal balance 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		 65,000us-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     0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
Recorded principal balance     $ 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember