XML 49 R75.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 4 - Loans and Allowance for Loan Losses (Details) - Loans by Credit Quality Indicators (USD $)
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Internal credit risk grade groupings:      
Loans $ 2,089,277,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome $ 1,053,243,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome $ 1,041,189,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Originated Loan [Member] | Commercial and Industrial [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 266,631,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		 208,151,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		  
Originated Loan [Member] | Commercial and Industrial [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 109,639,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		 76,237,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		  
Originated Loan [Member] | Commercial and Industrial [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 8,300,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		 1,985,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		  
Originated Loan [Member] | Commercial and Industrial [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Originated Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 11,242,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		 6,973,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		  
Originated Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 16,375,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		 25,535,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		  
Originated Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 2,209,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		 4,233,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		  
Originated Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Originated Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 190,656,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		 156,230,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		  
Originated Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 83,123,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		 103,066,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		  
Originated Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 17,979,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		 2,581,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		  
Originated Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Originated Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 285,035,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		 219,325,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		  
Originated Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 113,982,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		 122,717,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		  
Originated Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 11,960,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		 22,024,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		  
Originated Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Originated Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 12,394,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		 15,465,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		  
Originated Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 22,282,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		 19,469,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		  
Originated Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 1,382,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		 2,705,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		  
Originated Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Originated Loan [Member]      
Internal credit risk grade groupings:      
Loans 1,246,116,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		 1,053,243,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_OriginatedLoanMember		  
Acquired Loan [Member] | Commercial and Industrial [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 72,411,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		    
Acquired Loan [Member] | Commercial and Industrial [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 90,320,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		    
Acquired Loan [Member] | Commercial and Industrial [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 3,306,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		    
Acquired Loan [Member] | Commercial and Industrial [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Acquired Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 5,875,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		    
Acquired Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 14,472,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		    
Acquired Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 1,801,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		    
Acquired Loan [Member] | Commercial Vacant Land and Land Development and Residential Construction Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Acquired Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 39,496,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		    
Acquired Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 92,212,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		    
Acquired Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 6,922,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		    
Acquired Loan [Member] | Commercial Real Estate Owner Occupied Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Acquired Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 65,886,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		    
Acquired Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 78,103,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		    
Acquired Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 4,608,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		    
Acquired Loan [Member] | Commercial Real Estate Non Owner Occupied Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Acquired Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Grade 1 - 4 [Member]      
Internal credit risk grade groupings:      
Loans 35,858,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade1-4Member		    
Acquired Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Grade 5 - 7 [Member]      
Internal credit risk grade groupings:      
Loans 49,781,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade5-7Member		    
Acquired Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member] | Grade 8 - 9 [Member]      
Internal credit risk grade groupings:      
Loans 1,063,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= mbwm_Grade8-9Member		    
Acquired Loan [Member] | Commercial Real Estate Multi Family and Residential Rental Loan [Member]      
Internal credit risk grade groupings:      
Loans 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		  
Acquired Loan [Member]      
Internal credit risk grade groupings:      
Loans 843,161,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancialInstrumentAxis
= mbwm_AcquiredLoanMember		  
Commercial and Industrial [Member]      
Internal credit risk grade groupings:      
Loans 550,607,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		 286,373,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialAndIndustrialMember		  
Commercial Vacant Land and Land Development and Residential Construction Loan [Member]      
Internal credit risk grade groupings:      
Loans 51,974,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		 36,741,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember		  
Commercial Real Estate Owner Occupied Loan [Member]      
Internal credit risk grade groupings:      
Loans 430,388,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		 261,877,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateOwnerOccupiedLoanMember		  
Commercial Real Estate Non Owner Occupied Loan [Member]      
Internal credit risk grade groupings:      
Loans 559,574,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		 364,066,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember		  
Commercial Real Estate Multi Family and Residential Rental Loan [Member]      
Internal credit risk grade groupings:      
Loans $ 122,760,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember		 $ 37,639,000us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember