XML 23 R42.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Note 4 - Loans and Allowance for Loan Losses (Details) - Components of Loan Portfolio (USD $) | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2015 | Dec. 31, 2014 | Mar. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | $ 2,120,760,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome | $ 2,089,277,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |
Loans, percentage of portfolio | 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan | 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan |
Loans, percentage of change in loans | 1.50%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage |  |
Commercial and Industrial [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 434,211,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 384,570,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Loans, percentage of portfolio | 32.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 30.80%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Loans, percentage of change in loans | 12.90%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |  |
Commercial and Industrial [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 153,464,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 166,037,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Loans, percentage of portfolio | 19.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 19.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Loans, percentage of change in loans | (7.60%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |  |
Commercial and Industrial [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 587,675,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 550,607,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Loans, percentage of portfolio | 27.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember | 26.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |
Loans, percentage of change in loans | 6.70%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_CommercialAndIndustrialMember |  |
Vacant Land and Land Development and Residential Construction Loan [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 35,948,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 29,826,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Loans, percentage of portfolio | 2.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 2.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Loans, percentage of change in loans | 20.50%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |  |
Vacant Land and Land Development and Residential Construction Loan [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 20,102,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 22,148,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Loans, percentage of portfolio | 2.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 2.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Loans, percentage of change in loans | (9.20%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |  |
Vacant Land and Land Development and Residential Construction Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 56,050,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 51,974,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Loans, percentage of portfolio | 2.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember | 2.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |
Loans, percentage of change in loans | 7.80%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember |  |
Real Estate Owner Occupied Loan [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 302,379,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember | 291,758,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |
Loans, percentage of portfolio | 22.80%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember | 23.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |
Loans, percentage of change in loans | 3.60%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |  |
Real Estate Owner Occupied Loan [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 129,616,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember | 138,630,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |
Loans, percentage of portfolio | 16.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember | 16.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |
Loans, percentage of change in loans | (6.50%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |  |
Real Estate Owner Occupied Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 431,995,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember | 430,388,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |
Loans, percentage of portfolio | 20.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember | 20.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |
Loans, percentage of change in loans | 0.40%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateOwnerOccupiedLoanMember |  |
Real Estate Non Owner Occupied Loan [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 423,381,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember | 410,977,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |
Loans, percentage of portfolio | 31.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember | 33.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |
Loans, percentage of change in loans | 3.00%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |  |
Real Estate Non Owner Occupied Loan [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 142,771,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember | 148,597,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |
Loans, percentage of portfolio | 18.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember | 17.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |
Loans, percentage of change in loans | (3.90%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |  |
Real Estate Non Owner Occupied Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 566,152,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember | 559,574,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |
Loans, percentage of portfolio | 26.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember | 26.80%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |
Loans, percentage of change in loans | 1.20%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateNonOwnerOccupiedLoanMember |  |
Real Estate Multi Family and Residential Rental Loan [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 34,922,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember | 36,058,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |
Loans, percentage of portfolio | 2.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember | 2.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |
Loans, percentage of change in loans | (3.20%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |  |
Real Estate Multi Family and Residential Rental Loan [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 82,555,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember | 86,702,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |
Loans, percentage of portfolio | 10.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember | 10.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |
Loans, percentage of change in loans | (4.80%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |  |
Real Estate Multi Family and Residential Rental Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 117,477,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember | 122,760,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |
Loans, percentage of portfolio | 5.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember | 5.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |
Loans, percentage of change in loans | (4.30%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember |  |
Home Equity and Other [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 53,707,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember | 50,059,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |
Loans, percentage of portfolio | 4.10%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember | 4.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |
Loans, percentage of change in loans | 7.30%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |  |
Home Equity and Other [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 99,279,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember | 109,219,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |
Loans, percentage of portfolio | 12.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember | 13.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |
Loans, percentage of change in loans | (9.10%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |  |
Home Equity and Other [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 152,986,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember | 159,278,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |
Loans, percentage of portfolio | 7.20%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember | 7.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |
Loans, percentage of change in loans | (4.00%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_HomeEquityAndOtherMember |  |
1-4 Family Mortgages [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 44,165,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember | 42,868,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |
Loans, percentage of portfolio | 3.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember | 3.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |
Loans, percentage of change in loans | 3.00%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |  |
1-4 Family Mortgages [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 164,260,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember | 171,828,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |
Loans, percentage of portfolio | 20.80%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember | 20.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |
Loans, percentage of change in loans | (4.40%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |  |
1-4 Family Mortgages [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 208,425,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember | 214,696,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |
Loans, percentage of portfolio | 9.80%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember | 10.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |
Loans, percentage of change in loans | (2.90%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_OneToFourFamilyMortgagesMember |  |
Retail Loan [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 97,872,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember | 92,927,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |
Loans, percentage of portfolio | 7.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember | 7.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |
Loans, percentage of change in loans | 5.30%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |  |
Retail Loan [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 263,539,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember | 281,047,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |
Loans, percentage of portfolio | 33.30%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember | 33.40%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |
Loans, percentage of change in loans | (6.20%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |  |
Retail Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 361,411,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember | 373,974,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |
Loans, percentage of portfolio | 17.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember | 17.90%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |
Loans, percentage of change in loans | (3.40%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = mbwm_RetailLoanMember |  |
Commercial Portfolio Segment [Member] | Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 1,230,841,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 1,153,189,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 1,004,218,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember
Loans, percentage of portfolio | 92.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 92.50%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Loans, percentage of change in loans | 6.70%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Commercial Portfolio Segment [Member] | Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 528,508,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 562,114,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Loans, percentage of portfolio | 66.70%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 66.60%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Loans, percentage of change in loans | (6.00%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Commercial Portfolio Segment [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 1,759,349,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 1,715,303,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Loans, percentage of portfolio | 83.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 82.10%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Loans, percentage of change in loans | 2.60%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Originated Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | 1,328,713,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 1,246,116,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 1,066,796,000 us-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 | 6.60%mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |  |
Acquired Loan [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans (in Dollars) | $ 792,047,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember | $ 843,161,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |
Loans, percentage of portfolio | 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember | 100.00%mbwm_LoanPortfolioClassesAndSegmentsAsPercentageOfAggregateLoan / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |
Loans, percentage of change in loans | (6.10%)mbwm_LoansAndLeasesReceivableNetOfDeferredIncomeIncreaseDecreasePercentage / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |  |

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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=49124121&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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