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Note 4 - Loans and Allowance for Loan Losses (Details) - Loans by Credit Quality Indicators (USD $) | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
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Internal credit risk grade groupings: |  |  |
Loans | $ 2,089,277,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome | $ 1,053,243,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome | $ 1,041,189,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Originated Loan [Member] | Commercial and Industrial [Member] | Grade 1 - 4 [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 266,631,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade1-4Member | 208,151,000 us-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 | 109,639,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade5-7Member | 76,237,000 us-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 | 8,300,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade8-9Member | 1,985,000 us-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 | 384,570,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 286,373,000 us-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 | 11,242,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade1-4Member | 6,973,000 us-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 | 16,375,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade5-7Member | 25,535,000 us-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 | 2,209,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade8-9Member | 4,233,000 us-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 | 29,826,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 36,741,000 us-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 | 190,656,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade1-4Member | 156,230,000 us-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 | 83,123,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade5-7Member | 103,066,000 us-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 | 17,979,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade8-9Member | 2,581,000 us-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 | 291,758,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember | 261,877,000 us-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 | 285,035,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade1-4Member | 219,325,000 us-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 | 113,982,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade5-7Member | 122,717,000 us-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 | 11,960,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade8-9Member | 22,024,000 us-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 | 410,977,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember | 364,066,000 us-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 | 12,394,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade1-4Member | 15,465,000 us-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 | 22,282,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade5-7Member | 19,469,000 us-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 | 1,382,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember / us-gaap_InternalCreditAssessmentAxis = mbwm_Grade8-9Member | 2,705,000 us-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 | 36,058,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember | 37,639,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember |
Originated Loan [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 1,246,116,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 1,053,243,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Acquired Loan [Member] | Commercial and Industrial [Member] | Grade 1 - 4 [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 72,411,000 us-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 | 90,320,000 us-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 | 3,306,000 us-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 | 166,037,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 0 us-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 | 5,875,000 us-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 | 14,472,000 us-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 | 1,801,000 us-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 | 22,148,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 0 us-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 | 39,496,000 us-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 | 92,212,000 us-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 | 6,922,000 us-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 | 138,630,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember | 0 us-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 | 65,886,000 us-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 | 78,103,000 us-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 | 4,608,000 us-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 | 148,597,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember | 0 us-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 | 35,858,000 us-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 | 49,781,000 us-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 | 1,063,000 us-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 | 86,702,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember | 0 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember |
Acquired Loan [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 843,161,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember | 0 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |
Commercial and Industrial [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 550,607,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 286,373,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Commercial Vacant Land and Land Development and Residential Construction Loan [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 51,974,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 36,741,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialVacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Commercial Real Estate Owner Occupied Loan [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 430,388,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember | 261,877,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateOwnerOccupiedLoanMember |
Commercial Real Estate Non Owner Occupied Loan [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | 559,574,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember | 364,066,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateNonOwnerOccupiedLoanMember |
Commercial Real Estate Multi Family and Residential Rental Loan [Member] |  |  |
Internal credit risk grade groupings: |  |  |
Loans | $ 122,760,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember | $ 37,639,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialRealEstateMultiFamilyAndResidentialRentalLoanMember |

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- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5074-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 + Details
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