XML 28 R78.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans Modified as Troubled Debt Restructurings (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Commercial:    
Loans modified, number of contracts   10us-gaap_FinancingReceivableModificationsNumberOfContracts2
Loans modified, pre-modification recorded principal balance   $ 7,231,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Loans modified, post-modification recorded principal balance   7,231,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Commercial and Industrial [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		 3us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember
Loans modified, pre-modification recorded principal balance 5,994,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		 741,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember
Loans modified, post-modification recorded principal balance 6,094,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		 741,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember
Commercial and Industrial [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 7us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		  
Loans modified, pre-modification recorded principal balance 1,604,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		  
Loans modified, post-modification recorded principal balance 1,604,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialAndIndustrialMember		  
Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 0us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Loans modified, pre-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 3,610,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Loans modified, post-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 3,610,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 0us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Loans modified, pre-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Loans modified, post-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Commercial Real Estate Owner Occupied Loan [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
Loans modified, pre-modification recorded principal balance 16,787,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 715,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
Loans modified, post-modification recorded principal balance 16,787,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 715,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
Commercial Real Estate Owner Occupied Loan [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Loans modified, pre-modification recorded principal balance 1,619,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Loans modified, post-modification recorded principal balance 1,619,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Commercial Real Estate Non Owner Occupied Loan [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
Loans modified, pre-modification recorded principal balance 146,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 45,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
Loans modified, post-modification recorded principal balance 146,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 45,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
Commercial Real Estate Non Owner Occupied Loan [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Loans modified, pre-modification recorded principal balance 65,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Loans modified, post-modification recorded principal balance 65,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 0us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
Loans modified, pre-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 241,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
Loans modified, post-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 241,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 4us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Loans modified, pre-modification recorded principal balance 394,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Loans modified, post-modification recorded principal balance 394,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Commercial Portfolio Segment [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 5us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		 9us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember
Loans modified, pre-modification recorded principal balance 22,927,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		 5,352,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember
Loans modified, post-modification recorded principal balance 23,027,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		 5,352,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember
Commercial Portfolio Segment [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 14us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Loans modified, pre-modification recorded principal balance 3,682,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Loans modified, post-modification recorded principal balance 3,682,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Retail Home Equity and Other [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 0us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans modified, pre-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans modified, post-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Retail Home Equity and Other [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans modified, pre-modification recorded principal balance 26,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans modified, post-modification recorded principal balance 26,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Retail Home Equity and Other [Member]    
Commercial:    
Loans modified, number of contracts   0us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember
Loans modified, pre-modification recorded principal balance   0us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember
Loans modified, post-modification recorded principal balance   0us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailHomeEquityAndOtherMember
Retail 1-4 Family Mortgages [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 0us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans modified, pre-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans modified, post-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Retail 1-4 Family Mortgages [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans modified, pre-modification recorded principal balance 179,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans modified, post-modification recorded principal balance 179,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Retail 1-4 Family Mortgages [Member]    
Commercial:    
Loans modified, number of contracts   1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember
Loans modified, pre-modification recorded principal balance   1,879,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember
Loans modified, post-modification recorded principal balance   1,879,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_Retail1To4FamilyMortgagesMember
Retail Loan [Member] | Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 0us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		  
Loans modified, pre-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		  
Loans modified, post-modification recorded principal balance 0us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		  
Retail Loan [Member] | Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		  
Loans modified, pre-modification recorded principal balance 205,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		  
Loans modified, post-modification recorded principal balance 205,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember		  
Retail Loan [Member]    
Commercial:    
Loans modified, number of contracts   1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember
Loans modified, pre-modification recorded principal balance   1,879,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember
Loans modified, post-modification recorded principal balance   1,879,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= mbwm_RetailLoanMember
Originated Loan [Member]    
Commercial:    
Loans modified, number of contracts 5us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		  
Loans modified, pre-modification recorded principal balance 22,927,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		  
Loans modified, post-modification recorded principal balance 23,027,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		  
Acquired Loan [Member]    
Commercial:    
Loans modified, number of contracts 16us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		  
Loans modified, pre-modification recorded principal balance 3,887,000us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		  
Loans modified, post-modification recorded principal balance $ 3,887,000us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember