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Note 4 - Loans and Allowance for Loan Losses (Details) - Activity in Allowance for Loan Losses and the Recorded Investments in Loans (USD $) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014
Total loans: |  |  |
Loans | $ 2,120,760,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |  | $ 2,089,277,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Provision for loan losses | (400,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet | (1,900,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet |
Commercial Portfolio Segment [Member] | Originated Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 17,736,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 20,455,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Allowance for loan losses | 18,977,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 19,001,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Allowance for loan losses: individually evaluated for impairment | 10,158,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 9,508,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Allowance for loan losses: collectively evaluated for impairment | 8,819,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 9,493,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Total loans: |  |  |
Loans | 1,230,841,000 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 | 1,153,189,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember
Loans: individually evaluated for impairment | 44,257,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 29,883,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Loans: collectively evaluated for impairment | 1,186,584,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 974,335,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Provision for loan losses | (499,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | (1,454,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Charge-offs | (78,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | (586,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Recoveries | 1,818,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember | 586,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |
Commercial Portfolio Segment [Member] | Acquired Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 681,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Allowance for loan losses | 622,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Total loans: |  |  |
Loans | 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
Provision for loan losses | (60,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Charge-offs | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Recoveries | 1,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_CommercialPortfolioSegmentMember |  |
Commercial Portfolio Segment [Member] |  |  |
Total loans: |  |  |
Loans | 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
Retail Loan [Member] | Originated Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 1,487,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 2,358,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Allowance for loan losses | 1,235,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 1,957,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Allowance for loan losses: individually evaluated for impairment | 208,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 971,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Allowance for loan losses: collectively evaluated for impairment | 1,027,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 986,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Total loans: |  |  |
Loans | 97,872,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 62,578,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Loans: individually evaluated for impairment | 1,193,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 3,512,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Loans: collectively evaluated for impairment | 96,679,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 59,066,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Provision for loan losses | 79,000 us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | (434,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Charge-offs | (363,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | (2,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Recoveries | 32,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember | 35,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |
Retail Loan [Member] | Acquired Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 61,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |  |
Allowance for loan losses | 177,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |  |
Total loans: |  |  |
Provision for loan losses | 117,000 us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |  |
Charge-offs | (7,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |  |
Recoveries | 6,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = mbwm_RetailLoanMember |  |
Unallocated Financing Receivables [Member] | Originated Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 76,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember | 8,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loan losses | 39,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember | (4,000)us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loan losses: individually evaluated for impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loan losses: collectively evaluated for impairment | 39,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember | (4,000)us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Total loans: |  |  |
Provision for loan losses | (37,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember | (12,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Charge-offs | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Recoveries | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Unallocated Financing Receivables [Member] | Acquired Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 0 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |
Allowance for loan losses | 0 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |
Total loans: |  |  |
Provision for loan losses | 0 us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |
Charge-offs | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |
Recoveries | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember / us-gaap_FinancingReceivablePortfolioSegmentAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |
Originated Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 19,299,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 22,821,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Allowance for loan losses | 20,251,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 20,954,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Allowance for loan losses: individually evaluated for impairment | 10,366,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 10,479,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Allowance for loan losses: collectively evaluated for impairment | 9,885,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 10,475,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Total loans: |  |  |
Loans | 1,328,713,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 1,066,796,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 1,246,116,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember
Loans: individually evaluated for impairment | 45,450,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 33,395,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Loans: collectively evaluated for impairment | 1,283,263,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 1,033,401,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Provision for loan losses | (457,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | (1,900,000)us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Charge-offs | (441,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | (588,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Recoveries | 1,850,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember | 621,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_OriginatedLoanMember |
Acquired Loan [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Allowance for loan losses | 742,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |  |
Allowance for loan losses | 799,000 us-gaap_FinancingReceivableAllowanceForCreditLosses / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |  |
Total loans: |  |  |
Loans | 792,047,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |  | 843,161,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember
Provision for loan losses | 57,000 us-gaap_AllowanceForLoanAndLeaseLossesAdjustmentsNet / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |  |
Charge-offs | (7,000)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |  |
Recoveries | $ 7,000 us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery / us-gaap_FinancialInstrumentAxis = mbwm_AcquiredLoanMember |  |

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