Document And Entity Information Due after ten years, fair value Dividend yield Note To Financial Statement Details Textual Significant Accounting Policies Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block] Note 1 - Summary of Significant Accounting Policies Due in one year or less, amortized cost Note 3 - Securities Risk-free interest rate Note 4 - Loans and Allowance for Loan Losses Due in one year or less, fair value Note 5 - Premises and Equipment, Net Due from one to five years, fair value Note 6 - Mortgage Loan Servicing Due from five to ten years, fair value Collateralized Mortgage Backed Securities [Member] Note 7 - Core Deposit Intangible Assets, Net Note 8 - Deposits Note 9 - Securities Sold Under Agreements to Repurchase Note 10 - Federal Home Loan Bank Advances Note 11 - Federal Income Taxes Change in net unrealized gain/(loss) on securities available for sale, net of tax effect Note 12 - Stock-based Compensation us-gaap_DebtSecuritiesAvailableForSaleRestricted Debt Securities, Available-for-sale, Restricted Note 13 - Related Parties Expected stock price volatility Note 14 - Commitments and Off-Balance Sheet Risk Note 17 - Fair Values of Financial Instruments Note 18 - Fair Value Measurements Commercial Real Estate [Member] Note 19 - Earnings Per Share Note 20 - Subordinated Debentures Expected option life (Year) Note 21 - Regulatory Matters Grades 5-7 [Member] A credit rating between 5 and 7. Note 23 - Quarterly Financial Data (Unaudited) Grades 1-4 [Member] A credit rating between 1 and 4. Note 24 - Mercantile Bank Corporation (Parent Company Only) Condensed Financial Statements Note 1 - Summary of Significant Accounting Policies - Year-end Mortgage Loans Held for Sale (Details) Grades 8-9 [Member] A credit rating between 8 and 9. Note 3 - Securities - Available-for-sale Securities (Details) Note 3 - Securities - Securities in a Continuous Loss Position (Details) Note 3 - Securities - Debt Securities by Maturity (Details) Note 4 - Loans and Allowance for Loan Losses - Components of Loan Portfolio (Details) Note 4 - Loans and Allowance for Loan Losses - Acquired Impaired Loans Accretable Yield (Details) mbwm_AggregateIncreaseDecreaseInPercentageOfDeposits Total deposits, percent increase The percentage of increase or (decrease) during the period in deposit liabilities. Note 4 - Loans and Allowance for Loan Losses - Concentrations Within the Loan Portfolio (Details) Note 4 - Loans and Allowance for Loan Losses - Nonperforming Loans (Details) Note 4 - Loans and Allowance for Loan Losses - Age Analysis of Past Due Loans (Details) Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss Note 4 - Loans and Allowance for Loan Losses - Impaired Loans (Details) Granted (in dollars per share) Securities available for sale, continuous unrealized loss position, unrealized loss Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total Note 4 - Loans and Allowance for Loan Losses - Loans by Credit Quality Indicators (Details) Vested (in dollars per share) Forfeited (in dollars per share) Note 4 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) Note 4 - Loans and Allowance for Loan Losses - Activity in Allowance for Loan Losses and the Recorded Investments in Loans (Details) us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue Nonvested at beginning of year (in dollars per share) Nonvested at end of year (in dollars per share) us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod Forfeited (in shares) Note 4 - Loans and Allowance for Loan Losses - Loans Modified as Troubled Debt Restructurings (Details) Note 4 - Loans and Allowance for Loan Losses - Loans Modified As Troubled Debt Restructurings Within the Previous Twelve Months That Became Over 30 Days Past Due (Details) us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber Nonvested at beginning of year (in shares) Nonvested at end of year (in shares) Note 4 - Loans and Allowance for Loan Losses - Activity for Troubled Debt Restructurings (Details) Note 4 - Loans and Allowance for Loan Losses - Allowance Related to Troubled Debt Restructurings (Details) Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss Note 5 - Premises and Equipment, Net - Summary of Premises and Equipment (Details) US Government Agencies Debt Securities [Member] Note 6 - Mortgage Loan Servicing - Mortgage Loans Serviced for Others (Details) Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Summary of Deposits and Percentage Change in Deposits [Table Text Block] Tabular disclosure of deposits and the percentage change in deposits. Note 6 - Mortgage Loan Servicing - Activity for Capitalized Mortgage Loan Servicing Rights (Details) Note 6 - Mortgage Loan Servicing - Estimated Amortization (Details) us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod Vested (in shares) us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroupMortgage Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage Mortgage loans held for sale, net Note 7 - Core Deposit Intangible Assets, Net - Estimated Amortization Expense on Core Deposit Intangible Assets (Details) mbwm_AggregateLocalDepositLiabilities Total local deposits Value of liabilities related to local deposits. Note 8 - Deposits - Summary of Deposits (Details) Note 8 - Deposits - Maturity Distribution for Certificate of Deposits (Details) mbwm_OutOfAreaTimeDeposits100000AndOver Out-of-area time, $100,000 and over The aggregate amount of out-of-area time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more. Note 8 - Deposits - Certificates of Deposit with Balances of $100,000 or More (Details) mbwm_OutOfAreaTimeDepositsUnder100000 Out-of-area time, under $100,000 The aggregate amount of out-of-area time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000. Note 9 - Securities Sold Under Agreements to Repurchase - Securities Sold Under Agreement to Repurchase (Details) mbwm_PercentageOfNonInterestBearingDomesticDepositsToDepositsDemand Noninterest-bearing demand, percentage Percentage of money in noninterest-bearing domestic accounts that entitle the depositor to withdraw funds at any time without prior notice, also known as demand deposits. Note 10 - Federal Home Loan Bank Advances - Maturities of Currently Outstanding FHLB Advances (Details) mbwm_AggregateOutOfAreaTimeDeposits Total out-of-area deposits Value of liabilities related to out-of-area time deposits. Note 11 - Federal Income Taxes - Consolidated Income Tax Expense (Details) mbwm_PercentageOfDomesticTimeDeposits100000AndOver Local Time, $100,000 and over, percentage The percentage of domestic time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more. Note 11 - Federal Income Taxes - Effective Income Tax Rate Reconciliation (Details) mbwm_PercentageOfDomesticTimeDepositsUnder100000 Local Time, under $100,000, percentage The percentage of domestic time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000. Note 11 - Federal Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) mbwm_PercentageOfOutOfAreaTimeDepositUnder100000 Out-of-area time, under $100,000, percentage The percentage of out-of-area time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000. us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice Options exercisable at year-end (in dollars per share) mbwm_AggregatePercentageOfLocalDeposits Total local deposits, percentage Represents a percentage of domestic deposit liabilities. Note 12 - Stock-based Compensation - Summary of Restricted Stock Activity (Details) us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value mbwm_PercentageOfOutOfAreaTimeDeposits100000AndOver Out-of-area time, $100,000 and over, percentage The percentage of out-of-area time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more. Note 12 - Stock-based Compensation - Summary of Stock Option Activity (Details) us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Note 12 - Stock-based Compensation - Stock Option Valuation Assumptions (Details) Securities available for sale, continuous unrealized loss position Debt Securities, Available-for-sale, Unrealized Loss Position, Total mbwm_AggregatePercentageOfDeposits Total deposits, percentage Represents a percentage of total deposits. Note 12 - Stock-based Compensation - Summary of Options Outstanding (Details) Note 12 - Stock-based Compensation - Summary of Information Related to Options Outstanding (Details) Aggregate intrinsic value of stock options exercised mbwm_AggregatePercentageOfOutOfAreaDeposits Total out-of-area deposits, percentage Represents a percentage of out-of-area deposits Note 12 - Stock-based Compensation - Summary of Stock Option Grants and Exercises (Details) mbwm_PercentageOfIncreaseDecreaseInNonInterestBearingDemandDeposits Noninterest-bearing demand, percent increase Percentage of increase or (decrease) in noninterest-bearing domestic accounts that entitle the depositor to withdraw funds at any time without prior notice, also known as demand deposits. Note 13 - Related Parties - Loans Outstanding to Directors and Executive Officers (Details) Options exercisable at year-end (in shares) Note 14 - Commitments and Off-Balance Sheet Risk - Exposure to Credit Losses (Details) mbwm_PercentageOfIncreaseDecreaseInMoneyMarketDeposits Money market, percent increase Percentage of increase or (decrease) in interest-bearing domestic money market demand account deposit liabilities. mbwm_PercentageOfIncreaseDecreaseOfInterestBearingCheckingDeposits Interest-bearing checking, percent increase Percentage of increase or (decrease) in interest-bearing domestic checking deposit liabilities. Note 14 - Commitments and Off-balance-sheet Risk - Instruments Carried at Fair Values (Details) Securities available for sale, continuous unrealized loss position, less than 12 months mbwm_PercentageOfIncreaseDecreaseInDomesticTimeDepositsUnder100000 Local Time, under $100,000, percent increase (decrease) Percentage of increase or (decrease) in domestic time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000. Note 17 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) Weighted average per share fair value of stock options granted (in dollars per share) Note 18 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) Securities available for sale, continuous unrealized loss position, 12 months or more mbwm_PercentageOfIncreaseOrDecreaseOfSavingsDeposits Savings, percent increase Percentage of increase or (decrease) in interest-bearing domestic savings deposit liabilities. Saving deposits bear interest and have no stated maturity. mbwm_AggregatePercentageIncreaseDecreaseInLocalDeposits Total local deposits, percent increase The percentage of increase or (decrease) during the period in domestic deposit liabilities. Note 18 - Fair Values - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) Note 19 - Earnings Per Share - Computation of Earnings Per Share (Details) mbwm_PercentageOfIncreaseDecreaseInDomesticTimeDeposits100000AndOver Local Time, $100,000 and over, percent increase (decrease) Percentage of increase or (decrease) in domestic time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more mbwm_PercentageOfIncreaseDecreaseInOutOfAreaTime100000AndOver Out-of-area time, $100,000 and over, percent increase Percentage of increase or (decrease) in out-of-area time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more. Note 20 - Subordinated Debentures - Business Trusts (Details) mbwm_PercentageOfIncreaseDecreaseInOutOfAreaTimeUnder100000 Out-of-area time, under $100,000, percent increase Percentage of increase or (decrease) in out-of-area time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000. Note 21 - Regulatory Matters - Actual Capital Levels and Minimum Levels (Details) us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares Note 23 - Quarterly Financial Data (Unaudited) - Quarterly Financial Data (Unaudited) (Details) Note 24 - Mercantile Bank Corporation (Parent Company Only) Condensed Financial Statements - Condensed Balance Sheets (Details) mbwm_AggregatePercentageIncreaseDecreaseInOutOfAreaDeposits Total out-of-area deposits, percent increase The percentage of increase or (decrease) during the period in out-of-area deposit liabilities. Note 24 - Mercantile Bank Corporation (Parent Company Only) Condensed Financial Statements - Condensed Statements of Income (Details) Note 24 - Mercantile Bank Corporation (Parent Company Only) Condensed Financial Statements - Condensed Statement of Cash Flows (Details) Financial Instruments [Domain] us-gaap_LoansAndLeasesReceivableRelatedPartiesProceeds Repayments Notes To Financial Statements Notes To Financial Statements [Abstract] us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice Outstanding at beginning of year (in dollars per share) Outstanding at end of year (in dollars per share) Financial Instrument [Axis] New loans us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice Forfeited or expired (in dollars per share) us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice Granted (in dollars per share) No single maturity, fair value us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice Exercised (in dollars per share) Reclassification of stranded tax effect related to available for sale securities resulting from Tax Cuts and Jobs Act Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effects adjustment of a new accounting principle applied in the period of adoption. No single maturity, amortized cost us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber Outstanding at beginning of year (in shares) Outstanding at end of year (in shares) Loans, Notes, Trade and Other Receivables Disclosure [Text Block] us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod Forfeited or expired (in shares) us-gaap_PolicyTextBlockAbstract Accounting Policies us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield Balance at beginning of period Balance at end of period us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldDisposalsOfLoans Reductions (1) us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion Accretion income Net reclassification from nonaccretable to accretable us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance, Total mbwm_ReserveOrLiabilityBalanceForFinancialInstrumentsWithOffBalanceSheetRisk Reserve or Liability Balance for Financial Instruments With Off Balance Sheet Risk The carrying amount for the reserve or liability for financial instruments with off-balance sheet risk. us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Maturities of Currently Outstanding FHLB Advances [Table Text Block] Tabular disclosure of the maturities of currently outstanding Federal Home Loan Bank advances. us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Summary of Contractual Amounts of Financial Instruments With Off Balance Sheet Risk [Table Text Block] Tabular disclosure of contractual amounts of financial instruments with off-balance sheet risk. Additions us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1 Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Consumer Other Financing Receivable 1 [Member] Class of financing receivables related to other consumer financing receivables. us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage LIABILITIES AND SHAREHOLDERS' EQUITY Vesting [Axis] mbwm_CashFairValueDisclosure Cash Fair value disclosure of cash held by the company. Vesting [Domain] mbwm_AccruedInterestReceivableFairValueDisclosure Accrued interest receivable Fair value disclosure for interest which has been accrued but unpaid. Total assets Total assets Plan Name [Axis] Plan Name [Domain] Efficiency program-related costs Amount of expenses recognized by efficiency program during the period. us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Payroll processing The income generate from providing payroll processing services to external customers. us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1 Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Letter of credit fees Amount of fees and commissions from letter of credit. Tax benefit realized from stock option exercises Available-for-sale Securities [Member] Commitments Contingencies and Guarantees [Text Block] Impaired loans The fair value disclosure of impaired loans held by the company. Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Foreclosed assets The fair value disclosure of foreclosed assets held by the company. Other assets Equity Award [Domain] Award Type [Axis] us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization Finite-Lived Intangible Assets, Accumulated Amortization Core deposit intangible, net Finite-Lived Intangible Assets, Net, Ending Balance Standby Letters of Credit [Member] us-gaap_FiniteLivedCoreDepositsGross Finite-Lived Core Deposits, Gross Qualitative and Quantitative Information, Transferor's Continuing Involvement in Transferred Financial Assets, Transfer or Transferee [Domain] Loss Contingency, Nature [Domain] Qualitative and Quantitative Information, Transferor's Continuing Involvement, Transferred Financial Assets, by Transfer or Transferee [Axis] mbwm_TrustPreferredSecuritiesIncludedInTierOneCapital Trust Preferred Securities Included in Tier One Capital Trust preferred securities held by the trust that are included in Tier One Capital and subject to certain limitations. mbwm_MaximumRestrictedCoreElementAllowedInTierOneCapitalPercent Maximum Restricted Core Element Allowed in Tier One Capital Percent The maximum amount of restricted core elements allowed in tier one capital expressed as a percent. Loss Contingency Nature [Axis] mbwm_MaximumLevelOfConsolidatedAggregateAssetsAllowingForInclusionOfTrustPreferredSecuritiesInTierOneCapital Maximum Level of Consolidated Aggregate Assets Allowing for Inclusion of Trust Preferred Securities in Tier One Capital The maximum level of consolidated aggregate assets allowing for inclusion of trust preferred securities in Tier 1 Capital under the Dodd-Frank Act. Preferred securities outstanding Preferred Securities of Subsidiary Trust Trust preferred securities possesses characteristics of both equity and debt issues and are generally issued by bank holding companies. Less: accumulated depreciation Premises and equipment, net Total premises and equipment Goodwill Goodwill, Ending Balance Property, plant and equipment, gross mbwm_StockRepurchaseProgramAdditionalAuthorizedAmount Stock Repurchase Program Additional Authorized Amount Additional amount of stock repurchase plan authorized. Mercantile Bank Capital Trust I [Member] A business trust owned by the Company. Fund [Member] A pooled collateralized debt obligation. us-gaap_DerivativeFairValueOfDerivativeLiability Interest rate swap us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsBalance Valuation Allowance for Impairment of Recognized Servicing Assets, Balance, Ending Balance Bank [Member] This item represents the items associated with the Bank only. Common equity tier 1 capital minimum required for capital adequacy, ratio Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy to Risk Weighted Assets The minimum common equity tier one capital ratio (common equity tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. Derivative Instrument [Axis] Derivative Contract [Domain] Common equity tier 1 capital to be well capitalized, ratio Common equity tier 1 capital ratio (common equity tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. Fair value Securities available for sale Debt Securities, Available-for-sale, Total Securities available for sale Securities Sold under Agreements to Repurchase [Member] Investment in bank subsidiary Mortgage Loan Derivatives, Policy [Policy Text Block] Disclosure of accounting policy for its mortgage loan derivative instruments. Mortgage Loans Held for Sale [Table Text Block] Tabular disclosure of year-end mortgage loans held for sale. Equity in undistributed net income of subsidiary us-gaap_IncomeLossFromEquityMethodInvestments Equity in undistributed net income of subsidiary Mortgage loans held for sale Amount, before allowance to adjust to lower of cost or market, of mortgage loan receivables held-for-sale that are not part of a disposal group. Additions us-gaap_ServicingAssetAtAmortizedValueAdditions Bank Owned Life Insurance, Policy [Policy Text Block] Disclosure of accounting policy for bank owned life insurance. us-gaap_ServicingAssetAtAmortizedValueAmortization1 Amortized to expense Servicing Asset at Amortized Cost [Table Text Block] Income before income tax benefit and equity in undistributed net income of subsidiary Income before federal income tax expense mbwm_AllowanceToAdjustToLowerOfCostOrMarket Less: Allowance to adjust to lower of cost or market Amount of allowance to adjust mortgage loans receivable held for sale to lower of cost or market price. Federal income tax benefit Federal income tax expense Tax expense us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValuePrepaymentSpeed Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Prepayment Speed us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueExpectedCreditLosses Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Expected Credit Losses us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueWeightedAverageLife1 Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Weighted Average Life Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueDiscountRate Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Discount Rate us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held, Ending Balance us-gaap_DefinedContributionPlanCostRecognized Defined Contribution Plan, Cost us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Interest-earning deposits Concentrations Within Loan Portfolio [Table Text Block] Tabular disclosure of concentrations within the loan portfolio. Cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Commercial Real Estate Loans to Lessors of Non Residential Buildings [Member] Represents the company's commercial real estate loans to lessors of non-residential buildings. Salaries and benefits Cash and due from banks mbwm_FinancingReceivableAllowanceForCreditLossesReversalOfRecovery Recoveries Amount of reversal of recovery of financing receivables doubtful of collection that were previously charged off. Amendment Flag Use of Estimates, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] Reclassification, Policy [Policy Text Block] us-gaap_GainLossOnSaleOfPropertyPlantEquipment Net loss from sales and disposals of premises and equipment Current Fiscal Year End Date us-gaap_DebtAndEquitySecuritiesRealizedGainLoss Net (gain) loss from sales of available for sale securities us-gaap_GainLossOnSaleOfMortgageLoans Net gain on sales of mortgage loans held for sale Document Fiscal Period Focus Document Fiscal Year Focus Consolidation, Policy [Policy Text Block] mbwm_ReclassificationFromAOCIToRetainedEarningsCurrentPeriod Reclassification from AOCI to Retained Earnings, Current Period Amount of reclassification from AOCI to retained earnings during the current period. Document Period End Date Tier 1 capital to average assets, ratio Tier 1 capital to average assets minimum required for capital adequacy, ratio Entity Emerging Growth Company Tier 1 capital to average assets to be well capitalized, ratio Document Type Nature of Operation [Policy Text Block] Disclosure of accounting policy on nature of operations. mbwm_FairValueInputsDiscountFactor Fair Value Inputs, Discount Factor Discount factor used to further reduce the balance sheet carrying amount of property or other assets. Total capital to be well capitalized, ratio Entity Small Business Entity Shell Company Common equity tier 1, ratio Document Information [Line Items] Document Information [Table] Total capital, ratio Total capital minimum required for capital adequacy, ratio Capital Required for Capital Adequacy to Risk Weighted Assets Entity Public Float Mortgage Loans Serviced for Others [Table Text Block] Tabular disclosure on mortgage loan portfolios serviced for others. Entity Filer Category Federa lHome Loan Bank [Member] Represent Federal Home Loans Bank. Tier 1 capital, ratio Entity Current Reporting Status Mortgage Loan Servicing [Text Block] The entire disclosure for mortgage loans serviced for others. Tier 1 capital minimum required for capital adequacy, ratio Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Entity Voluntary Filers mbwm_ContinuingInvolvementWithTransferredFinancialAssetsCustodialEscrowBalance Continuing Involvement with Transferred Financial Assets Custodial Escrow Balance Custodial escrow balances maintained in connection with serviced loans. Tier 1 capital to be well capitalized, ratio Entity Well-known Seasoned Issuer 2019 mbwm_MortgageServicingRightsAmortizationExpenseNextTwelveMonths Amount of amortization expense for mortgage servicing rights expected to be recognized during the next fiscal year following the latest fiscal year. Total capital, amount 2020 mbwm_MortgageServicingRightsAmortizationExpenseYearTwo Amount of amortization expense for mortgage servicing rights to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Total capital minimum required for capital adequacy, amount Federal Home Loan Mortgage Corporation [Member] Represent Federal Home Loan Mortgage Corporation. Total capital to be well capitalized, amount 2023 mbwm_MortgageServicingRightsAmortizationExpenseYearFive Amount of amortization expense for mortgage servicing rights expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Thereafter mbwm_MortgageServicingRightsAmortizationExpenseAfterYearFive Amount of amortization expense for mortgage servicing rights expected to be recognized after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. 2021 mbwm_MortgageServicingRightsAmortizationExpenseYearThree Amount of amortization expense for mortgage servicing rights expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. 2022 mbwm_MortgageServicingRightsAmortizationExpenseYearFour Amount of amortization expense for mortgage servicing rights expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Bank owned life insurance Tier 1 capital to average assets, amount Tier 1 capital to average assets, minimum required for capital adequacy, amount Tier 1 capital to average assets to be well capitalized, amount us-gaap_ServicingAssetAtFairValueAmount Servicing Asset at Fair Value, Amount, Ending Balance Contractual Maturities of Certificates of Deposits of More than Specified Amount [Table Text Block] Tabular disclosure of the contractual maturities of certificates of deposits of more than specified amount. Common equity tier 1, amount Statement of Comprehensive Income [Abstract] us-gaap_ServicingAssetAtAmortizedValue Balance at beginning of year Balance at end of year Common equity tier 1 minimum required for capital adequacy, amount Contractual Maturities of Certificates of Deposits [Table Text Block] Tabular disclosure of the maturity distribution for certificates of deposit at year-end. Common equity tier 1 capital to be well capitalized, amount Entity Central Index Key Tier 1 capital, amount Entity Registrant Name Tier 1 capital minimum required for capital adequacy, amount Tier 1 capital to be well capitalized, amount Entity [Domain] Legal Entity [Axis] mbwm_EffectiveIncomeTaxReconciliationBankOwnedLifeInsurance Bank owned life insurance Amount of the difference between reported income tax expense (benefit) and expected tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from bank owned life insurance that is exempt from income taxes. Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] us-gaap_FinancingReceivableAllowanceForCreditLosses Beginning balance Ending balance mbwm_DeferredTaxAssetsFairValueWriteDownsOnForeclosedProperties Fair value write-downs on foreclosed properties Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from write-downs on foreclosed properties. Regulatory Capital Requirements under Banking Regulations [Text Block] mbwm_DeferredTaxLiabilitiesBusinessCombinationAdjustments Business combination adjustments Amount of deferred tax liability attributable to taxable temporary differences from business combination. mbwm_DeferredTaxAssetsNonAccrualLoanInterestIncome Nonaccrual loan interest income Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from nonaccrual loan interest income. us-gaap_ForeclosedAssets Repossessed Assets, Total Entity Common Stock, Shares Outstanding (in shares) Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Income Advertising us-gaap_LoansAndLeasesReceivableNetReportedAmount Loans, net us-gaap_LoansAndLeasesReceivableDeferredIncome Loans and Leases Receivable, Deferred Income, Total Loans Ending balance us-gaap_LoansAndLeasesReceivableAllowance Allowance for loan losses Trading Symbol Data processing Expenses Occupancy Total expenses mbwm_InterestAndOtherOperatingExpenses The total amount of interest and other operating expenses for the period. mbwm_SharebasedCompensationArrangementBySharebasedPaymentAwardMinimumNumberOfSharesForMinimumVestingRights Share-based Compensation Arrangement by Share-based Payment Award, Minimum Number of Shares for Minimum Vesting Rights Represents the benchmark for the minimum number of shares awarded required for minimum vesting rights. mbwm_SharebasedCompensationArrangementBySharebasedPaymentAwardMaximumNumberOfSharesForMaximumVestingRights Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares for Maximum Vesting Rights Represents the benchmark for the maximum number of shares awarded required for maximum vesting rights. Thereafter us-gaap_TableTextBlock Notes Tables Directors and Executive Officers [Member] Represents the Directors and Executive officers of the company. mbwm_RelatedPartyDepositsAndRepurchaseAgreements Related Party Deposits and Repurchase Agreements Represents the balances of related party deposits and repurchase agreements. mbwm_LoanCommitmentsToRelatedParties Loan Commitments to Related Parties Represents the amount of loan commitments to related parties of the Company. First Bank Plans [Member] Compensation plans that originated with Firstbank. Mercantile Plans [Member] Compensation plans that originated with Mercantile. Real Estate Dependent Loans and Foreclosed Assets [Member] Information pertaining to both real estate dependent loans and foreclosed assets. 2020 2021 2022 Federal Home Loan Bank stock 2023 mbwm_InterestExpenseDeferredCompensationPlan Interest Expense, Deferred Compensation Plan Represents the amount of interest expense incurred during the period related to deferred compensation plans. Stock Purchase Plan [Member] The Mercantile Bank Corporation Employee Stock Purchase Plan of 2014. mbwm_CapitalConservationBuffer Capital Conservation Buffer An additional amount held in risk-based capital designed to ensure that banks build up capital buffers outside periods of stress which can be drawn down as losses are incurred. The requirement is based on simple capital conservation rules designed to avoid breaches of minimum capital requirements. us-gaap_CashCashEquivalentsAndFederalFundsSold Total cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Other operating expenses us-gaap_OtherCostAndExpenseOperating Schedule of Share Based Compensation Arrangement by Share Based Payment Award Options Information Related to Stock Option Grants and Exercised [Table Text Block] Schedule of share based compensation arrangement by share based payment award options information related to stock option grants and exercised. us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateAtPeriodEnd Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Interest Rate at Period End mbwm_FairValueDiscountOfSubordinatedDebenturesRelatedToAssumedBusinessTrustsAtTimeAfMerger Fair Value Discount of Subordinated Debentures Related to Assumed Business Trusts at Time af Merger Represents the fair value discount of subordinated debentures related to assumed business trusts at the time of the merger. mbwm_NumberOfBusinessTrusts Number of Business Trusts Represents the Company's business trusts. mbwm_TermDebtSecuredByRealEstateBalloonPaymentPeriod Term Debt, Secured by Real Estate Balloon Payment, Period The period in which term debt becomes secured by a balloon payment. Exercise Price Range 1 [Member] Range 1 in a range of of exercise prices. us-gaap_FederalHomeLoanBankAdvancesBranchOfFHLBBankInterestRate Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate mbwm_AmortizationOfFairValueDiscountRelatedToSubordinatedDebenturesOfAssumedBusinessTrusts Amortization of Fair Value Discount Related to Subordinated Debentures of Assumed Business Trusts Represents the annual amortization of the fair value discount related to subordinated debentures of assumed business trusts over a period of time. Interest expense us-gaap_InterestExpense Total interest expense mbwm_AmortizationPeriodOfFairValueDiscountRelatedToSubordinatedDebenturesOfAssumedBusinessTrusts Amortization Period of Fair Value Discount Related to Subordinated Debentures of Assumed Business Trusts Represents the amortization period of the fair value discount related to subordinated debentures of assumed business trusts. us-gaap_InterestExpenseDebt Interest Expense, Debt, Total Exercise Price Range 3 [Member] Range 3 in a range of of exercise prices. Other Debt and Equity Securities [Member] Investments in debt and equity securities classified as other. Exercise Price Range 2 [Member] Range 2 in a range of of exercise prices. Firstbank Capital Trust I [Member] A business trust owned by the Company. mbwm_InterestRatesOnLoansSecuredByNonRealEstateCollateral Interest Rates on Loans, Secured by Non-real Estate Collateral Stated interest rates on loans that are secured by non-real estate collateral. us-gaap_DisclosureTextBlockAbstract Notes to Financial Statements Federal Home Loan Bank Advances, Disclosure [Text Block] mbwm_AmortizationPeriodForTermDebtSecuredByRealEstate Amortization Period for Term Debt, Secured by Real Estate Amortization period for the payments related to a credit facility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Derivative Instruments and Hedging Activities Disclosure [Text Block] Subsequent Event [Member] Firstbank Capital Trust III [Member] A business trust owned by the Company. Firstbank Capital Trust IV [Member] A business trust owned by the Company. Schedule of Share-based Compensation Shares Authorized Under Stock Option Plans Information Related to Option Outstanding [Table Text Block] Schedule of share based compensation shares authorized under stock option plans information related to option outstanding. Firstbank Capital Trust II [Member] A business trust owned by the Company. Subsequent Event Type [Axis] Federal Home Loan Bank advances us-gaap_InterestExpenseFederalHomeLoanBankAndFederalReserveBankAdvancesLongTerm Subsequent Event Type [Domain] mbwm_TermDebtSecuredByNonRealEstateCollateralMaturityPeriod Term Debt Secured, by Non-real Estate Collateral Maturity Period Period of time between issuance and maturity of term debt secured by non-real estate collateral, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Short-term borrowings Pension and Other Postretirement Benefits Disclosure [Text Block] mbwm_AmountOfFederalReserveRequired Amount of Federal Reserve Required Amount of federal reserve requirement at period end that can be met with vault cash or deposits at a Federal Reserve Bank. Subordinated debentures and other borrowings us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive Thereafter us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsSavings Savings, percentage us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo 2020 Deposits Fair Value of Financial Instruments, Policy [Policy Text Block] us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree 2021 us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsChecking Interest-bearing checking, percentage us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour 2022 us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive 2023 us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsMoneyMarket Money market, percentage Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths 2019 Title of Individual [Axis] Relationship to Entity [Domain] Earnings Per Share, Policy [Policy Text Block] Interest expense Total income us-gaap_Revenues Comprehensive Income, Policy [Policy Text Block] Income Tax, Policy [Policy Text Block] Interest and dividends from subsidiaries us-gaap_InterestAndDividendIncomeOperating Total interest income Interest income Other interest-earning assets Three months to six months Six months to twelve months Over twelve months us-gaap_TimeDeposits100000OrMore Total certificates of deposit Intangible Assets Disclosure [Text Block] Up to three months Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] In three to four years In four to five years Securities, taxable Securities, tax-exempt Problem asset costs The costs that are associated with problem assets. In one year or less In one to two years In two to three years Advertising Cost, Policy, Expensed Advertising Cost [Policy Text Block] Loans, including fees us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Revenue from Contract with Customer [Policy Text Block] Noninterest-bearing Noninterest-bearing demand us-gaap_DeferredTaxAssetsValuationAllowance Valuation allowance Commitments and Contingencies, Policy [Policy Text Block] mbwm_NetGainLossFromSaleAndValuationWriteDownOfForeclosedAssets Net gain from sales and valuation write-downs of foreclosed assets The net gain or loss resulting from the sale and valuation write-down of foreclosed assets. us-gaap_DeferredTaxAssetsNet Deferred tax asset after valuation allowance Interest income us-gaap_DeferredTaxAssetsLiabilitiesNet Total net deferred tax asset Other us-gaap_DeferredTaxAssetsOther us-gaap_InterestBearingDomesticDepositMoneyMarket Money market us-gaap_InterestBearingDomesticDepositSavings Savings Goodwill and Intangible Assets, Policy [Policy Text Block] us-gaap_DeferredTaxAssetsGross Deferred tax asset before valuation allowance us-gaap_DeferredIncomeTaxLiabilities Deferred tax liability us-gaap_InterestBearingDomesticDepositChecking Interest-bearing checking Other income Total noninterest income Noninterest income us-gaap_DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross Unrealized loss on securities us-gaap_TimeDepositsAtOrAboveFDICInsuranceLimit Time Deposits, at or Above FDIC Insurance Limit us-gaap_DeferredTaxAssetsDeferredIncome Deferred loan fees Earnings on bank owned life insurance Earnings on bank owned life insurance Deposit Liabilities Disclosures [Text Block] Noninterest income: us-gaap_RepurchaseAgreementCounterpartyWeightedAverageMaturityOfAgreements1 Repurchase Agreement Counterparty, Weighted Average Maturity of Agreements Special Dividend [Member] Related to a special dividend. us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss Net interest income after provision for loan losses Provision for loan losses Schedule of Repurchase Agreements [Table Text Block] us-gaap_PropertyPlantAndEquipmentUsefulLife Property, Plant and Equipment, Useful Life Net interest income Net interest income us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses Allowance for loan losses us-gaap_NumberOfOperatingSegments Number of Operating Segments Furniture and Fixtures [Member] us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits Deferred compensation us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost Stock compensation Building and Building Improvements [Member] Building [Member] Land and Land Improvements [Member] First Bank Employees [Member] Represents First Bank employees. us-gaap_DeferredTaxAssetsCapitalLossCarryforwards Deferred Tax Assets, Capital Loss Carryforwards Real Estate Dependent Loans and Foreclosed Assets Estimated Selling Costs [Member] Represents real estate dependent loans and foreclosed assets, estimated selling costs. Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block] Property, Plant and Equipment, Policy [Policy Text Block] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Deposit Account [Member] Mortgage Banking [Member] Credit and Debit Card [Member] ASSETS Net cash for financing activities Net cash from financing activities Transfers and Servicing of Financial Assets, Policy [Policy Text Block] invest_DerivativeNotionalAmount Derivative, Notional Amount us-gaap_NetCashProvidedByUsedInOperatingActivities Net cash from operating activities us-gaap_DeferredTaxLiabilitiesOther Other Net cash for investing activities Net cash for investing activities Net change in cash and cash equivalents Net change in cash and cash equivalents us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets Core deposit intangible Derivatives, Policy [Policy Text Block] Repurchase and Resale Agreements Policy [Policy Text Block] Net cash from operating activities Marketable Securities, Policy [Policy Text Block] us-gaap_DeferredTaxLiabilitiesMortgageServicingRights Mortgage loan servicing rights Related allowance Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block] us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment Depreciation us-gaap_DeferredTaxLiabilitiesPrepaidExpenses Prepaid expenses us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod Impaired Financing Receivable, Interest Income, Cash Basis Method, Total mbwm_InterestIncomeOnCommercialAndMortgageLoansDiscontinuedPeriod Interest Income on Commercial and Mortgage Loans Discontinued Period Number of days past due when interest income on commercial and mortgage loans is discontinued unless the loans are well-secured and in process of collection. mbwm_MaximumDelinquencyPeriodForConsumerAndCreditCardLoansToBeChargedOff Maximum Delinquency Period for Consumer and Credit Card Loans to be Charged Off Maximum number of days delinquent for consumer and credit card loans to be charged off. us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod Impaired Financing Receivable, Interest Income, Accrual Method, Total With no related allowance recorded, principal balance us-gaap_PaymentsOfDividendsCommonStock Payment of cash dividends to common shareholders With related allowance recorded, principal balance Total principal balance With no related allowance recorded, average recorded principal balance With related allowance recorded, average recorded principal balance Total average recorded principal balance With no related allowance recorded, unpaid principal balance With related allowance recorded, unpaid principal balance Total unpaid principal balance Other expense us-gaap_NoninterestExpense Total noninterest expenses us-gaap_PaymentsForRepurchaseOfCommonStock Repurchase of common stock us-gaap_ProceedsFromStockPlans Employee stock purchase plan Effect of federal tax law change Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability Furniture and equipment rent, depreciation and maintenance FDIC insurance costs Proceeds from stock option exercises, net of cashless exercises Noninterest expense Residential Real Estate [Member] Dividend reinvestment plan Dividend reinvestment plan Deferred income tax expense (benefit) Collateral [Domain] mbwm_BusinessCombinationBranchesAcquired Business Combination Branches Acquired The number of banking branches acquired in a business combination. Firstbank Corporation [Member] The entity of Firstbank Corporation. mbwm_BusinessAcquisitionConversionOfStockPerShare Business Acquisition Conversion of Stock Per Share The number of shares that each share of the acquiree is converted into shares of the acquirer. Collateral [Axis] Current expense Class of Financing Receivable, Type [Domain] us-gaap_PaymentsForRepurchaseOfTrustPreferredSecurities Payments for Repurchase of Trust Preferred Securities Repurchase of trust preferred securities Unallocated Financing Receivables [Member] Class of Financing Receivable, Type [Axis] Financing Receivable Portfolio Segment [Domain] Commercial Portfolio Segment [Member] Consumer Portfolio Segment [Member] Financing Receivable Portfolio Segment [Axis] Comprehensive Income (Loss) Note [Text Block] Loans and Leases Receivable, Mortgage Banking Activities, Policy [Policy Text Block] Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block] Finance, Loan and Lease Receivables, Held for Investments, Foreclosed Assets Policy [Policy Text Block] Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block] Finance, Loan and Lease Receivables, Held-for-investment, Policy [Policy Text Block] us-gaap_RepaymentsOfFederalHomeLoanBankBorrowings Maturities of Federal Home Loan Bank advances Cash and Cash Equivalents, Policy [Policy Text Block] us-gaap_UnrecognizedTaxBenefits Unrecognized Tax Benefits, Ending Balance Schedule of Subordinated Borrowing [Table Text Block] Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Subordinated Borrowing [Axis] Subordinated Borrowing, Name [Domain] Subordinated Borrowings Disclosure [Text Block] us-gaap_CommonStockDividendsPerShareDeclared Common Stock, Dividends, Per Share, Declared Cash dividends per common share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Condensed Financial Information of Parent Company Only Disclosure [Text Block] Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Mortgage loans serviced for others us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding Average shares and dilutive potential common shares (in shares) Asset Class [Axis] Asset Class [Domain] Statement of Financial Position [Abstract] Diluted earnings per common share (in dollars per share) Diluted (in dollars per share) Earnings per share diluted (in dollars per share) Weighted average common shares outstanding (in shares) Weighted average common shares outstanding for basic earnings per common share (in shares) Business Acquisition [Axis] Basic earnings per common share (in dollars per share) Basic (in dollars per share) Earnings per share basic (in dollars per share) Proceeds from Federal Home Loan Bank advances Business Acquisition, Acquiree [Domain] Statement of Cash Flows [Abstract] Statement of Stockholders' Equity [Abstract] Net decrease in securities sold under agreements to repurchase Schedule of Financing Receivables, Non Accrual Status [Table Text Block] Quarterly Financial Information [Table Text Block] us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued Business Acquisition, Equity Interest Issued or Issuable, Number of Shares mbwm_BusinessCombinationDebtAssumedNumberOfTrusts Business Combination Debt Assumed Number of Trusts The number of trusts for which debt assumed in a business combination are payable to. Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Due from five to ten years, weighted average yield The weighted average yield of a securities portfolio with due dates before 5 years and before 10 years. Due from one to five years, weighted average yield The weighted average yield of a securities portfolio with due dates after 1 year and before 5 years. No single maturity, weighted average yield The weighted average yield of a securities portfolio with no single maturity date defined. Due after ten years, weighted average yield The weighted average yield of a securities portfolio with due dates after 10 years. Weighted average yield The aggregate weighted average yield of a securities portfolio. Net decrease in time deposits Net (decrease) increase in all other deposits us-gaap_LoansAndLeasesReceivableRelatedParties Loans and Leases Receivable, Related Parties, Ending Balance Beginning balance Ending balance Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques [Table Text Block] Other us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval Cash flows from financing activities us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate Effect of federal tax law change Change in valuation allowance us-gaap_IncomeTaxReconciliationTaxExemptIncome Tax-exempt interest us-gaap_PaymentsToAcquireLifeInsurancePolicies Purchases of bank owned life insurance Proceeds from bank owned life insurance cash value release and death benefits Dividends [Axis] Dividends [Domain] mbwm_MinimumNumberOfDaysPastDueAtPeriodEndForLoansModifiedAsTroubledDebtRestructurings Minimum Number of Days Past Due at Period End For Loans Modified as Troubled Debt Restructurings Represents the minimum number of days past due at period end for loans modified as troubled debt restructurings. Originated Loan [Member] A loan that was originated by the entity. Net capital investment into subsidiaries Acquired Loan [Member] A loan that was acquired by the entity. Class of Stock [Axis] Vacant Land and Land Development and Residential Construction Loan [Member] Segment of the company's total financing receivables related to vacant land and land development and residential construction receivables. Commercial and Industrial [Member] Financing arrangement that represents a contractual right to receive money either on demand or on fixed or determinable dates related to commercial and industrial receivables. Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Real Estate Owner Occupied Loan [Member] Segment of the company's total financing receivables related to real estate owner occupied receivables. us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Total Real Estate Multi Family and Residential Rental Loan [Member] Segment of the company's total financing receivables related to real estate multi-family and residential rental loan receivables. Real Estate Non Owner Occupied Loan [Member] Segment of the company's total financing receivables related to real estate non owner occupied receivables. Retail Portfolio Segment [Member] Portfolio segment of the company's total financing receivables related to retail receivables. Tax at statutory rate Income Tax Disclosure [Text Block] Home Equity and Other [Member] Segment of the company's total financing receivables related to home equity and other receivables. One to Four Family Mortgages [Member] Segment of the company's total financing receivables related to 1-4 family mortgages. Percent of portfolio Percent of portfolio Loan portfolio classes and segments expressed as a percentage of the companies aggregate loans. Period increase (decrease) The percentage of increase or (decrease) during the period in loans and leases receivable net of deferred income. us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Schedule of Mortgage Servicing Rights Future Amortization Expense [Table Text Block] Tabular disclosure of the amount of amortization expense expected to be recorded in succeeding fiscal years for mortgage servicing rights. Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block] Internal Credit Assessment [Axis] Proceeds from maturities, calls and repayments of securities available for sale Internal Credit Assessment [Domain] us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount Business Acquisition, Goodwill, Expected Tax Deductible Amount Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Accretable Yield Movement [Table Text Block] Roll forward of the accretable yield for certain loans acquired with deteriorated credit quality not accounted for as debt securities. Total nonperforming loans Amount of financing receivables which are past due 90 days or more and still accruing interest and nonaccrual loans. us-gaap_PaymentsForProceedsFromProductiveAssets Purchases of premises and equipment, net Credit Facility [Axis] Credit Facility [Domain] Add: Dilutive effects of share-based awards (in shares) Transfers from loans to foreclosed assets us-gaap_FinancingReceivableModificationsRecordedInvestment Beginning Balance Ending Balance Federal income taxes us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 Number of Contracts us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2 Pre- Modification Recorded Principal Balance us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 Post- Modification Recorded Principal Balance Supplemental disclosures of cash flows information us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 Recorded Principal Balance us-gaap_FinancingReceivableModificationsNumberOfContracts2 Number of Contracts Impaired Financing Receivables [Table Text Block] Troubled Debt Restructurings on Financing Receivables [Table Text Block] Core Deposits [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Net income Net income Net income Net income attributable to common shares Financial Instrument Performance Status [Axis] Financial Instrument Performance Status [Domain] Nonperforming Financial Instruments [Member] Loans past due 90 days or more still accruing interest Financing Receivable Credit Quality Indicators [Table Text Block] Restricted Stock [Member] Performance Shares [Member] Current loans Employee Stock Option [Member] Past due loans Nonaccrual loans Financing Receivables, 30 to 59 Days Past Due [Member] Financing Receivables, 60 to 89 Days Past Due [Member] Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Past Due Financing Receivables [Table Text Block] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] Proceeds from sales of foreclosed assets Business Combination Disclosure [Text Block] us-gaap_PaymentsForProceedsFromLoansAndLeases Loan originations and payments, net Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] us-gaap_PaymentsToAcquireFederalHomeLoanBankStock Purchases of Federal Home Loan Bank stock Cash flows from investing activities Earnings per common share: Earnings Per Share [Text Block] Related Party Transactions Disclosure [Text Block] Schedule of Related Party Transactions [Table Text Block] us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax Tax effect of unrealized holding gains (losses) on securities available for sale Gain on trust preferred securities repurchase Gain on trust preferred securities repurchase Amount of gain (loss), from the difference between the repurchase price of the trust preferred securities initially issued by the entity or its subsidiaries and the net carrying amount of the debt at the time of its repurchase. mbwm_DiscountAccretionOnAcquiredLoans Accretion of acquired loans Represents the accretion of acquired loans recorded as interest income during the period. Junior Subordinated Debt [Member] us-gaap_AllocatedShareBasedCompensationExpense Allocated Share-based Compensation Expense, Total us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment Ending balance: individually evaluated for impairment us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment Ending balance: collectively evaluated for impairment Ending balance: individually evaluated for impairment Ending balance: collectively evaluated for impairment Recoveries us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs Charge-offs Comprehensive income us-gaap_ComprehensiveIncomeNetOfTax Comprehensive income Change in other liabilities Accrued interest and other liabilities Common stock, shares outstanding (in shares) Allowance for Credit Losses on Financing Receivables [Table Text Block] Weighted average interest rate during the year Interest rate margin Debt Instrument, Basis Spread on Variable Rate us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets Other assets us-gaap_DebtInstrumentRepurchasedFaceAmount Debt Instrument, Repurchased Face Amount us-gaap_DebtInstrumentRepurchaseAmount Debt Instrument, Repurchase Amount us-gaap_DividendsCommonStockCash Cash dividends London Interbank Offered Rate (LIBOR) [Member] us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet Accrued interest receivable Variable Rate [Domain] Variable Rate [Axis] us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue Stock-based compensation expense Quarterly Financial Information [Text Block] us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements us-gaap_StockRepurchasedDuringPeriodShares Stock Repurchased During Period, Shares us-gaap_StockRepurchasedAndRetiredDuringPeriodValue Share repurchase program Share repurchase program (in shares) Reclassification of equity securities related to ASU 2016-01 adoption The amount of adjustment to equity related to the ASU 2016-01 adoption. us-gaap_StockRepurchasedDuringPeriodValue Stock Repurchased During Period, Value us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan Dividend reinvestment plan Dividend reinvestment plan (in shares) mbwm_NumberOfUnconsolidatedBusinessTrustsFormedToIssueTrustPreferredSecurities Number of Unconsolidated Business Trusts Formed to Issue Trust Preferred Securities The number of unconsolidated business trusts formed to issue trust preferred securities. Employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Stock option exercises (in shares) Exercised (in shares) us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity Line of Credit Facility, Remaining Borrowing Capacity mbwm_NetGainLossFromSaleAndValuationWriteDownOfFormerBankPremises Net (gain) loss from sales and valuation write-downs of former bank premises The net gain or loss resulting from the sale and valuation write-down of former bank premises. Employee stock purchase plan Proceeds from sales of former bank premises The cash inflow from sale of former bank premises. us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity Line of Credit Facility, Maximum Borrowing Capacity us-gaap_PaymentsForOriginationOfMortgageLoansHeldForSale Origination of mortgage loans held for sale Stock option exercises Director [Member] Executive Officer [Member] Transfers from bank premises to other real estate owned Value transferred from bank premises to real estate owned (REO) in noncash transactions. Related Party [Axis] Related Party [Domain] Proceeds from sales of mortgage loans held for sale Consolidated Entities [Member] us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Stock grants to directors for retainer fees Stock grants to directors (in shares) Stock Issued During Period, Shares, Issued for Services Total liabilities and shareholders’ equity Total liabilities and shareholders’ equity Reported Value Measurement [Member] Maximum daily balance during the year Average daily balance during the year Allowance Related to Loans Categorized as Troubled Debt Restructurings [Table Text Block] Tabular disclosure of the allowance related to loans categorized as troubled debt restructurings by loan class. Bank Board Members [Member] Represents the Bank Board members of the company. Weighted average interest rate at year-end Retained earnings Accumulated other comprehensive loss Trouble Debt Restructuring Activity [Table Text Block] Tabular disclosure of activity for loans modified as troubled debt restructurings. Includes charge-offs, payments, transfers to Other Real Estate and net additions/deletions. Net change in: All Other States and Their Political Subdivisions [Member] States and their political subdivisions other than the State of Michigan and its political subdivision. State of Michigan and All Its Political Subdivisions [Member] Securities in the state of Michigan and all its political subdivisions. us-gaap_OperatingLeaseLiability Operating Lease, Liability, Total US Government Agency Debt Obligations and Mortgage Backed Securities [Member] This category includes information about debt securities issued by the United states and securities which are mortgage backed. mbwm_AccruedInterestPayableFairValueDisclosure Accrued interest payable Fair value portion of accrued interest payable. us-gaap_OperatingLeaseRightOfUseAsset Operating Lease, Right-of-Use Asset Deferred expense Municipal General Obligation Bonds [Member] This category includes information about debt securities classified as municipal general obligation bonds. Stock grants to directors for retainer fee Stock grants to directors for retainer fees Municipal Revenue Bonds [Member] This category includes information about debt securities classified as municipal revenue bonds. us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax, Ending Balance Stock-based compensation expense us-gaap_ShareBasedCompensation Depreciation and amortization Due in one year or less, weighted average yield The weighted average yield of securities portfolio with due dates in less than 1 year. Total Total us-gaap_Depreciation Depreciation, Total us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure Federal Home Loan Bank advances us-gaap_LoansHeldForSaleFairValueDisclosure Loans held for sale us-gaap_CashAndCashEquivalentsFairValueDisclosure Cash equivalents us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure Securities sold under agreements to repurchase us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations Subordinated debentures mbwm_FinancingReceivableModifiedAsTroubledDebtRestructuringsChargeOffs Charge-Offs Reflects the amount of the charge-off related to a troubled debt restructuring. mbwm_FinancingReceivableModifiedAsTroubledDebtRestructuringsPayments Payments The cash inflow associated with a financing receivable classified as a troubled debt restructuring. Net Additions/Deletions A financing receivable which had its terms modified during the period and is now considered a troubled restructuring. mbwm_FinancingReceivableModifiedAsTroubledDebtRestructuringsTransferToOtherRealEstate Transfers to ORE The transfer of a financing receivable classified as a troubled debt restructuring to other real estate. Grant Per Annum Starting One Year From Date of Grant [Member] Represents the percentage of grant per annum starting vesting one year from date of grant. Fair Value, Measurements, Nonrecurring [Member] Common stock, no par value; 40,000,000 shares authorized; 16,534,256 shares outstanding at December 31, 2018 and 16,592,125 shares outstanding at December 31, 2017 Troubled Debt Restructurings on Financing Receivables with in Previous Twelve Months that Became Over Thirty Days Past Due [Table Text Block] Tabular disclosure for troubled debt restructurings on financing receivables within the previous twelve months that became over thirty days past due. Adjustments to reconcile net income to net cash from operating activities: Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Common stock, shares authorized (in shares) Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Common stock, par value (in dollars per share) us-gaap_CommonStockCapitalSharesReservedForFutureIssuance Common Stock, Capital Shares Reserved for Future Issuance Range [Domain] Maximum [Member] Minimum [Member] Weighted Average [Member] Product and Service [Axis] Product and Service [Domain] Range [Axis] Preferred stock, no par value; 1,000,000 shares authorized; 0 shares outstanding at December 31, 2018 and December 31, 2017 Preferred stock, shares outstanding (in shares) Interest Preferred stock, par value (in dollars per share) Property, Plant and Equipment Disclosure [Text Block] Property, Plant and Equipment [Table Text Block] Preferred stock, shares authorized (in shares) Portion at Fair Value Measurement [Member] [Default] Estimate of Fair Value Measurement [Member] Federal Home Loan Bank of Indianapolis [Member] Measurement Basis [Axis] Federal Home Loan Bank Branch [Domain] Fair Value, Inputs, Level 3 [Member] Fair Value Hierarchy and NAV [Domain] Fair Value, Inputs, Level 1 [Member] Federal Home Loan Bank Branch [Axis] Fair Value, Inputs, Level 2 [Member] Fair Value Hierarchy and NAV [Axis] Cash flows from operating activities Statement [Line Items] Standby letters of credit, contract amount Contractual amounts of financial instruments with off-balance sheet risk Standby letters of credit, carrying value AOCI Attributable to Parent [Member] Shareholders' equity us-gaap_InvestmentInFederalHomeLoanBankStockFairValueDisclosure Federal Home Loan Bank stock Schedule of Fair Value, Off-balance Sheet Risks [Table Text Block] Debt Security Category [Axis] us-gaap_LoansReceivableFairValueDisclosure Loans, net Other than Temporary Impairment, Credit Losses Recognized in Earnings, Categories of Investments [Domain] Adjustments for New Accounting Principle, Early Adoption [Member] Fair Value Disclosures [Text Block] Fair Value, by Balance Sheet Grouping [Table Text Block] Liabilities Total liabilities Counterparty Name [Axis] Counterparty Name [Domain] us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent Deferred Compensation Liability, Current and Noncurrent, Total Accounting Standards Update 2016-02 [Member] Parent Company [Member] us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total Consolidated Entities [Axis] Consolidated Entities [Domain] Type of Adoption [Domain] Accrued interest and other liabilities Adjustments for New Accounting Pronouncements [Axis] Condensed Cash Flow Statement [Table Text Block] Condensed Balance Sheet [Table Text Block] Condensed Income Statement [Table Text Block] Retained Earnings [Member] us-gaap_TreasuryStockAcquiredAverageCostPerShare Treasury Stock Acquired, Average Cost Per Share Common Stock Including Additional Paid in Capital [Member] us-gaap_StockRepurchaseProgramAuthorizedAmount1 Stock Repurchase Program, Authorized Amount Preferred Stock [Member] Equity Components [Axis] Equity Component [Domain] Federal Home Loan Bank advances Long-term Federal Home Loan Bank Advances, Total Other Liabilities [Member] Subordinated debentures Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust, Total Balance Sheet Location [Axis] Balance Sheet Location [Domain] Securities sold under agreements to repurchase Outstanding balance at year-end 2019 srt_MortgageLoansOnRealEstateInterestRate SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Interest Rate us-gaap_ValuationAllowancesAndReservesBalance SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount, Ending Balance us-gaap_DepositsFairValueDisclosure Deposits us-gaap_PaymentsToAcquireAvailableForSaleSecurities Purchases of securities available for sale Proceeds from sales of securities available for sale Proceeds from Sale of Available-for-sale Securities, Total Scenario, Forecast [Member] Statement [Table] Scenario [Axis] Scenario, Unspecified [Domain] us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter Operating Leases, Future Minimum Payments, Due Thereafter us-gaap_OperatingLeasesFutureMinimumPaymentsDue Operating Leases, Future Minimum Payments Due, Total us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourAndFiveYears Operating Leases, Future Minimum Payments, Due in Four and Five Years, Total us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoAndThreeYears Operating Leases, Future Minimum Payments, Due in Two and Three Years, Total us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet Interest rate swap agreement us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent Total other comprehensive income (loss) 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Period, Net of Tax us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax Tax effect of fair value of interest rate swap Loan Origination Commitments [Member] Unused lines of Credit [Member] Shareholders’ equity Total shareholders’ equity Balances Balances Other comprehensive income (loss): mbwm_DomesticTimeDeposits100000OrMore Local Time, $100,000 and over Amount of local time deposit liabilities, including certificates of deposit, in denominations of $100,000 or more. mbwm_DeomesticTimeDepositsLessThan100000 Local Time, under $100,000 Amount of domestic time deposit liabilities, including certificates of deposit, in denominations of less than $100,000. us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax Securities available for sale, gross unrealized losses Outstanding Weighted Average Exercise Price (in dollars per share) Securities available for sale, gross unrealized gains Average remaining option term (Year) Interest Rate Swap [Member] Exercisable Number (in shares) Exercisable Weighted Average Exercise Price (in dollars per share) Maximum exercise price (in dollars per share) Amortized cost us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis Debt Securities, Available-for-sale, Amortized Cost, Total Outstanding Number (in shares) Due from one to five years, amortized cost Exercise Price Range [Axis] Due from five to ten years, amortized cost Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] Due after ten years, amortized cost Minimum exercise price (in dollars per share)