XML 146 R69.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 4 - Loans and Allowance for Loan Losses (Details) - Components of Loan Portfolio (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) $ 2,089,277,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome $ 1,053,243,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome $ 1,041,189,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Loans, percentage of portfolio 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan  
Loans, percentage of change in loans 98.40%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage    
Originated Loan [Member] | Commercial and Industrial [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 384,570,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 286,373,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Loans, percentage of portfolio 30.80%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 27.20%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Loans, percentage of change in loans 34.30%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		    
Originated Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 29,826,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 36,741,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Loans, percentage of portfolio 2.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 3.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Loans, percentage of change in loans (18.80%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		    
Originated Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 291,758,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 261,877,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Loans, percentage of portfolio 23.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 24.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Loans, percentage of change in loans 11.40%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		    
Originated Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 410,977,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 364,066,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Loans, percentage of portfolio 33.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 34.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Loans, percentage of change in loans 12.90%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		    
Originated Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 36,058,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 37,639,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Loans, percentage of portfolio 2.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 3.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Loans, percentage of change in loans (4.20%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		    
Originated Loan [Member] | Commercial Portfolio Segment [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 1,153,189,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 986,696,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Loans, percentage of portfolio 92.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 93.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Loans, percentage of change in loans 16.90%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		    
Originated Loan [Member] | Retail Home Equity and Other [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 50,059,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		 35,080,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans, percentage of portfolio 4.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		 3.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans, percentage of change in loans 42.70%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		    
Originated Loan [Member] | Retail 1-4 Family Mortgages [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 42,868,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		 31,467,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans, percentage of portfolio 3.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		 3.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans, percentage of change in loans 36.20%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		    
Originated Loan [Member] | Retail Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 92,927,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		 66,547,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		  
Loans, percentage of portfolio 7.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		 6.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		  
Loans, percentage of change in loans 39.60%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		    
Originated Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 1,246,116,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		 1,053,243,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		  
Loans, percentage of portfolio 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		  
Loans, percentage of change in loans 18.30%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		    
Acquired Loan [Member] | Commercial and Industrial [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 166,037,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Loans, percentage of portfolio 19.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 22,148,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Loans, percentage of portfolio 2.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 138,630,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Loans, percentage of portfolio 16.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 148,597,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Loans, percentage of portfolio 17.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 86,702,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Loans, percentage of portfolio 10.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Commercial Portfolio Segment [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 562,114,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Loans, percentage of portfolio 66.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Retail Home Equity and Other [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 109,219,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans, percentage of portfolio 13.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Retail 1-4 Family Mortgages [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 171,828,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans, percentage of portfolio 20.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		     
Loans, percentage of change in loans       
Acquired Loan [Member] | Retail Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 281,047,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		  
Loans, percentage of portfolio 33.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		     
Loans, percentage of change in loans       
Acquired Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 843,161,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		  
Loans, percentage of portfolio 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		     
Loans, percentage of change in loans       
Commercial and Industrial [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 550,607,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 286,373,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Loans, percentage of portfolio 26.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 27.20%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Loans, percentage of change in loans 92.30%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		    
Commercial Vacant Land and Land Development and Residential Construction Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 51,974,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 36,741,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Loans, percentage of portfolio 2.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 3.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Loans, percentage of change in loans 41.50%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		    
Commercial Real Estate Owner Occupied Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 430,388,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 261,877,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Loans, percentage of portfolio 20.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 24.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Loans, percentage of change in loans 64.30%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		    
Commercial Real Estate Non Owner Occupied Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 559,574,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 364,066,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Loans, percentage of portfolio 26.80%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 34.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Loans, percentage of change in loans 53.70%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		    
Commercial Real Estate Multi Family and Residential Rental Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 122,760,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 37,639,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Loans, percentage of portfolio 5.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 3.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		  
Loans, percentage of change in loans 226.20%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		    
Commercial Portfolio Segment [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 1,715,303,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 986,696,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 968,506,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
Loans, percentage of portfolio 82.10%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 93.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Loans, percentage of change in loans 73.80%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		    
Retail Home Equity and Other [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 159,278,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		 35,080,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans, percentage of portfolio 7.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		 3.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		  
Loans, percentage of change in loans 354.00%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailHomeEquityAndOtherMember		    
Retail 1-4 Family Mortgages [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) 214,696,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		 31,467,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans, percentage of portfolio 10.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		 3.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		  
Loans, percentage of change in loans 582.30%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_Retail1To4FamilyMortgagesMember		    
Retail Loan [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans (in Dollars) $ 373,974,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		 $ 66,547,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		 $ 72,683,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember
Loans, percentage of portfolio 17.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		 6.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember		  
Loans, percentage of change in loans 462.00%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_RetailLoanMember