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Significant Accounting Policies (Policies) | 12 Months Ended
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Dec. 31, 2023
Accounting Policies [Abstract] |
Consolidation, Policy [Policy Text Block] | Principles of Consolidation: The consolidated financial statements include the accounts of Mercantile Bank Corporation (“Mercantile”) and its subsidiaries, Mercantile Bank (“our bank”) and Mercantile Community Partners LLC ("MCP"), and of Mercantile Insurance Center, Inc. (“our insurance company”), a subsidiary of our bank, after elimination of significant intercompany transactions and accounts. Mercantile has five separate business trusts: Mercantile Bank Capital Trust I, Firstbank Capital Trust I, Firstbank Capital Trust II, Firstbank Capital Trust III and Firstbank Capital Trust IV (“our trusts”). Our trusts were formed to issue trust preferred securities. We issued subordinated debentures to our trusts in return for the proceeds raised from the issuance of the trust preferred securities. Our trusts are not consolidated, but instead we report the subordinated debentures issued to the trusts as liabilities.
Nature of Operation [Policy Text Block] | Nature of Operations: Mercantile was incorporated on July 15, 1997 to establish and own the bank based in Grand Rapids, Michigan. Our bank began operations on December 15, 1997. We completed the merger of Firstbank Corporation (“Firstbank”), a Michigan corporation with approximately $1.5 billion in total assets and 46 branch locations, into Mercantile as of June 1, 2014. Mercantile is a financial holding company whose principal activity is the ownership and management of our bank and operates a single significant business segment. Our bank is a community-based financial institution. Our bank’s primary deposit products are checking, savings, and term certificate accounts, and its primary lending products are commercial loans, residential mortgage loans, and instalment loans. Substantially all loans are secured by specific items of collateral including business assets, real estate or consumer assets. Commercial loans are expected to be repaid from cash flow from operations of businesses. Real estate loans are secured by commercial or residential real estate. We have no material foreign loans or significant overdraft balances. Our bank’s loan accounts and retail deposits are primarily with customers located in the communities in which we have bank office locations. As an alternative source of funds, our bank has also issued certificates of deposit to depositors outside of its primary market areas. Substantially all revenues are derived from banking products and services and investment securities. While we monitor the revenue streams of the various products and services offered, we manage our business on the basis of one operating segment, banking. Our insurance company acquired an existing shelf insurance agency effective April 15, 2002. An Agency and Institution Agreement was entered into among our insurance company, our bank and Hub International for the purpose of providing programs of mass marketed personal lines of insurance. Insurance product offerings include private passenger automobile, homeowners, personal inland marine, boat owners, recreational vehicle, dwelling fire, umbrella policies, small business and life insurance products, all of which are provided by and written through companies that have appointed Hub International as their agent. To date, we have not provided the insurance products noted above and currently have no plans to do so. We have evaluated subsequent events for potential recognition and/or disclosure through the date these financial statements were issued.
Use of Estimates, Policy [Policy Text Block] | Use of Estimates: To prepare financial statements in conformity with accounting principles generally accepted in the United States of America, management makes estimates and assumptions based on available information. These estimates and assumptions affect the amounts reported in the financial statements and the disclosures provided, and actual results could differ. The allowance for credit losses and the fair values measurements are particularly subject to change.
Effect of Covid-19 Pandemic, Policy [Policy Text Block] | Coronavirus Pandemic: Although virtually all related restrictions have been terminated, impacts remain across national and global economies due to the pandemic of coronavirus disease 2019 (“Covid-19”) caused by severe acute respiratory syndrome coronavirus 2 (the “Coronavirus Pandemic”). Overall, the Coronavirus Pandemic has caused a sustained global economic slowdown of varying durations across different industries. The Coronavirus Pandemic has had a significant impact on our financial condition and operating results since its onset in March, 2020. Federal government stimulus programs resulted in a massive increase to the money supply, providing significant inflationary pressures that the Federal Reserve’s Federal Open Market Committee (“FOMC”) has been attempting to manage through substantial increases in the federal funds rate since March, 2022. In addition, we experienced significant growth in liquidity during 2021 and 2022 as federal government stimulus monies were deposited by program recipients, providing for sizable impacts to our operating performance as well as our capital and liquidity positions during both years. The Paycheck Protection Program (“PPP”) reflected a substantial expansion of the Small Business Administration’s 100% guaranteed 7(a) loan program. The PPP provided 100% guaranteed loans to cover specific operating costs. PPP loans were eligible to be forgiven based upon certain criteria. Any remaining balance after forgiveness is maintained at the 100% guarantee for the duration of the loan. The interest rate on the loan is fixed at 1.00%, with the financial institution receiving a loan origination fee from the Small Business Administration. The loan origination fees, net of the direct origination costs, are accreted into interest income on loans using the level yield methodology. The program ended on August 8, 2020. We originated approximately 2,200 loans aggregating $554 million. As of December 31, 2023, we recorded forgiveness transactions on all but four loans aggregating $0.1 million. The Consolidated Appropriations Act, 2021 authorized an additional $284 billion in Second Draw PPP loans (“Second Draw”). This program ended on May 31, 2021. Under the Second Draw, we originated approximately 1,200 loans aggregating $209 million. As of December 31, 2023, we recorded forgiveness transactions on all but five loans aggregating $0.2 million.
Cash and Cash Equivalents, Policy [Policy Text Block] | Cash and Cash Equivalents and Cash Flow Reporting: Cash and cash equivalents include cash on hand, demand deposits with other financial institutions, short-term investments and federal funds sold. Cash flows are reported net for customer loan and deposit transactions, interest-earning deposits invested with other financial institutions and short-term borrowings with maturities of 90 days or less.
Marketable Securities, Policy [Policy Text Block] | Debt Securities: Debt securities classified as held to maturity are carried at amortized cost when management has the positive intent and ability to hold them to maturity. Debt securities available for sale consist of bonds which might be sold prior to maturity due to a number of factors, including changes in interest rates, prepayment risks, yield, availability of alternative investments or liquidity needs. Debt securities classified as available for sale are reported at their fair value. For available for sale debt securities in an unrealized loss position, we first assess whether we intend to sell, or if it is more likely than not that we will be required to sell the security before recovery of the amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the debt security’s amortized cost basis is written down to fair value through income with the establishment of an allowance. For debt securities available for sale that do not meet the aforementioned criteria, we evaluate whether any decline in fair value is due to credit loss factors. In making this assessment, we consider any changes to the rating of the security by a rating agency and adverse conditions specifically related to the issuer of the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of the cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance is recognized in other comprehensive income. Changes in the allowance are recorded as provisions for (or reversal of) credit loss expense. Losses are charged against the allowance when the collectability of an available for sale debt security is confirmed or when either of the criteria regarding intent or requirement to sell is met. At December 31, 2023, there was no allowance related to the available for sale debt securities portfolio. Interest income includes amortization of purchase premiums and accretion of discounts. Premiums and discounts on securities are amortized or accreted on the level-yield method without anticipating prepayments, except for mortgage-backed securities where prepayments are anticipated. Gains and losses on sales are recorded on the trade date and determined using the specific identification method. Accrued interest receivable on available for sale debt securities totaling $2.6 million and $2.5 million at December 31, 2023 and 2022, respectively, was reported in other assets on the Consolidated Balance Sheets. Management has made the accounting policy election to exclude accrued interest receivable on available for sale securities from the estimate of credit losses as accrued interest is written off in a timely manner when deemed uncollectible.
Federal Home Loan Bank Stock, Policy [Policy Text Block] | Federal Home Loan Bank Stock: Our bank owns stock of the Federal Home Loan Bank of Indianapolis ("FHLBI"). FHLBI is a governmental sponsored entity that requires banks to invest in their nonmarketable stock as a condition of membership. FHLBI members are required to own a certain amount of stock based on the level of borrowings and other factors, and may invest in additional amounts. FHLBI stock is carried at cost, classified as a restricted security, and periodically evaluated for impairment based on ultimate recovery of par value. The ability to redeem the shares owned is dependent on the redemption practice of the FHLBI. Dividends are recorded in income on the ex-dividend date.
Financing Receivable, Held-for-Investment [Policy Text Block] | Loans: Loans that we have the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at the principal balance outstanding outstanding adjusted for partial charge-offs, the allowance, net of deferred loan fees and costs. Interest income on loans is accrued over the term of the loans primarily using the simple interest method based on the principal balance outstanding. Accrued interest is included in other assets in the Consolidated Balance Sheets. Loan origination fees and certain direct costs incurred to extend credit are deferred and amortized over the term of the loan or loan commitment period as an adjustment to the related loan yield. Interest income is accrued on the unpaid principal balance. Loan origination fees, net of certain direct origination costs, are deferred and recognized in interest income using the level-yield method without anticipating prepayments. Net unamortized deferred loan costs amounted to $2.4 million and $1.0 million at December 31, 2023 and 2022, respectively. Interest income on commercial loans and mortgage loans is discontinued at the time the loan is 90 days delinquent unless the loan is well-secured and in process of collection. Consumer and credit card loans are typically charged off no later than when they are 120 days past due. Past due status is based on the contractual terms of the loan. In all cases, loans are placed on nonaccrual or charged off at an earlier date if collection of principal and interest is considered doubtful. All interest accrued but not received for loans placed on nonaccrual is reversed against interest income. Interest received on such loans is accounted for on the cash-basis or cost-recovery method, until qualifying for return to accrual. Loans are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured.
Commercial Loan Participations [Policy Text Block] | Commercial Loan Participations: As part of our credit risk administration practices and to manage exposure limits, we engage in commercial loan participations with other financial institutions from time-to-time. In all instances, the commercial loans are participated at par with no loan yield adjustments; therefore, no gain or loss on sale, or servicing right, is recorded. We retain a large portion of the loan exposure and continue to service the lending relationship. Commercial loan participations aggregated $46.7 million and $33.5 million as of December 31, 2023 and 2022, respectively.
Financing Receivable, Held-for-Sale [Policy Text Block] | Loans Held for Sale: Mortgage loans originated and intended for sale in the secondary market are carried at the lower of aggregate cost or fair value, as determined by outstanding commitments from investors. Net unrealized losses, if any, are recorded as a valuation allowance and charged to earnings. Mortgage loans held for sale are generally sold with servicing rights retained. Gains and losses on sales of mortgage loans are based on the difference between the selling price and the carrying value of the related mortgage loan sold, which is reduced by the cost allocated to the servicing right. We generally lock in the sale price to the purchaser of the mortgage loan at the same time we make an interest rate commitment to the borrower. Year-end mortgage loans held for sale were as follows:
(Dollars in thousands) |  | 2023 |  |  | 2022 |
Mortgage loans held for sale |  | $ | 18,607 |  |  | $ | 3,565 |
Less: Allowance to adjust to lower of cost or market |  |  | 0 |  |  |  | 0 |
Mortgage loans held for sale, net |  | $ | 18,607 |  |  | $ | 3,565 |
Mortgage Loan Derivatives, Policy [Policy Text Block] | Mortgage Loan Derivatives: We enter into forward contracts and interest rate lock commitments in the ordinary course of business, which are accounted for as derivatives. The derivatives are not designated as hedges and are carried at fair value. The net gain or loss on derivatives is included in mortgage banking activities in the Consolidated Statements of Income. The net balance of mortgage loan derivatives aggregated to a liability of less than $0.1 million at December 31, 2023 and an asset of less than $0.1 million as of December 31, 2022.
Mortgage Banking Activity [Policy Text Block] | Mortgage Banking Activities: Mortgage loan servicing rights are recognized as assets based on the allocated value of retained servicing rights on mortgage loans sold. Mortgage loan servicing rights are carried at the lower of amortized cost or fair value and are expensed in proportion to, and over the period of, estimated net servicing revenues. Impairment is evaluated based on the fair value of the rights using groupings of the underlying mortgage loans as to interest rates. Any impairment of a grouping is reported as a valuation allowance. Servicing fee income is recorded for fees earned for servicing mortgage loans. The fees are based on a contractual percentage of the outstanding principal or a fixed amount per loan and are recorded as income when earned. Amortization of mortgage loan servicing rights is netted against mortgage loan servicing income and recorded in mortgage banking activities in the Consolidated Statements of Income. Accounting for mortgage servicing rights is based on the class of mortgage servicing rights. We have identified four classes of mortgage servicing rights based on the initial term of the underlying mortgage loans: 10 years, 15 years, 20 years and 30 years. We distinguish between these classes based on the differing sensitivities to the change in value from changes in mortgage interest rates. Mortgage servicing rights are initially recorded at fair value, and then are accounted for using the amortization method. Netted against mortgage banking income, mortgage servicing rights amortization expense is reported as noninterest income in the Consolidated Statements of Income. Mortgage servicing rights amortization is determined by amortizing the mortgage servicing rights balance in proportion to, and over the period of the estimated future net servicing income, of the underlying mortgage loans. Interest rate risk, prepayment risk and default risk are inherent in mortgage servicing rights valuation. Interest rate changes largely drive prepayment rates. Refinance activity generally increases as interest rates decline. A significant decrease in interest rates beyond expectation could cause a decline in the value of mortgage servicing rights. On the contrary, borrowers are less likely to refinance or prepay their mortgage loans if interest rates increase, which would extend the duration of the underlying mortgage loans and the associated mortgage servicing rights value would likely rise. Because of these risks, discount rates and prepayment speeds are used to estimate the fair value of mortgage servicing rights.
Troubled Debt Restructuring [Policy Text Block] | Troubled Debt Restructurings: The accounting guidance for troubled debt restructurings by creditors in Subtopic 310-40, Receivables – Troubled Debt Restructurings by Creditors was eliminated upon our adoption of ASU No. 2022-02 Financial Instruments – Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures which was effective January 1, 2023. ASU No. 2022-02 eliminated troubled debt restructurings recognition and measurement guidance and, instead, requires that entities evaluate (consistent with the accounting for other loan modifications) whether the modification represents a new loan or a continuation of an existing loan. See further discussion on ASU No. 2022-02 within "Recent Accounting Changes Adopted." Prior to the adoption of ASU No. 2022-02, a loan was accounted for as a troubled debt restructuring if we, for economic or legal reasons, granted a concession to a borrower considered to be experiencing financial difficulties that we would not otherwise consider. A troubled debt restructuring may have involved the receipt of assets from the debtor in partial or full satisfaction of the loan, or a modification of terms such as a reduction of the stated interest rate or balance of the loan, a reduction of accrued interest, an extension of the maturity date or renewal of the loan at a stated interest rate lower than the current market rate for a new loan with similar risk, or some combination of these concessions. Troubled debt restructurings could be in either accrual or nonaccrual status. Nonaccrual troubled debt restructurings were included in nonperforming loans. Accruing troubled debt restructurings were generally excluded from nonperforming loans as it was considered probable that all contractual principal and interest due under the restructured terms would be collected. In accordance with previous accounting guidance, loans modified as troubled debt restructurings were, by definition, considered to be impaired loans. Impairment for these loans were measured on a loan-by-loan basis. Certain loans modified as troubled debt restructurings may have been previously measured for impairment under a general allowance methodology (i.e., pooling), thus at the time the loan is modified as a troubled debt restructuring the allowance may have been impacted by the difference between the results of these two measurement methodologies. Loans modified as troubled debt restructurings that subsequently default are factored into the determination of the allowance in the same manner as other defaulted loans. Our bank has chosen to continue to individually assess loans previously identified as troubled debt restructurings for allowance for credit losses purposes; thus, there was no change to the allowance for credit losses upon adoption.
Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] | Allowance for Credit Losses (“Allowance”): The allowance is a valuation account that is deducted from the loans’ amortized cost basis to present the net amount expected to be collected on the loans. The allowance is increased by provision expense and decreased by charge-offs, net of recoveries of amounts previously charged-off. Loans are charged-off against the allowance when we believe the uncollectibility of a loan balance is confirmed. The allowance is measured on a collective pool basis when similar risk characteristics exist and on an individual basis when a loan exhibits unique risk characteristic which differentiate the loan from other loans within the loan segments. Loan segments are further discussed in Note 3 - Loans and Allowance for Credit Losses. The “remaining life methodology” is utilized for substantially all loan pools. This non-discounted cash flow approach projects an estimated future amortized cost basis based on current loan balance and repayment terms. Our historical loss rate is then applied to future loan balances at the instrument level based on remaining contractual life adjusted for amortization, prepayment and default to develop a baseline lifetime loss. The baseline lifetime loss is adjusted for changes in macroeconomic conditions over the reasonable and supportable forecast and reversion periods via a series of macroeconomic forecast inputs, such as gross domestic product, unemployment rates, interest rates, credit spreads, stock market volatility and property price indices, to quantify the impact of current and forecasted economic conditions on expected loan performance. Reasonable and supportable economic forecasts have to be incorporated in determining expected credit losses. The forecast period represents the time frame from the current period end through the point in time that we can reasonably forecast and support entity and environmental factors that are expected to impact the performance of our loan portfolio. Ideally, the economic forecast period would encompass the contractual terms of all loans; however, the ability to produce a forecast that is considered reasonable and supportable becomes more difficult or may not be possible in later periods. The contractual term generally excludes potential extensions, renewals and modifications. Subsequent to the end of the forecast period, we revert to historical loan data based on an ongoing evaluation of each economic forecast in relation to then current economic conditions as well as any developing loan loss activity and resulting historical data. We are not required to develop and use our own economic forecast model, and elect to utilize economic forecasts from third-party providers that analyze and develop forecasts of the economy for the entire United States at least quarterly. During each reporting period, we also consider the need to adjust the historical loss rates as determined to reflect the extent to which we expect current conditions and reasonable and supportable economic forecasts to differ from the conditions that existed for the period over which the historical loss information was determined. These qualitative adjustments may increase or decrease our estimate of expected future credit losses. Our qualitative factors include:
| o | Changes in lending policies and procedures
| o | Changes in the nature and volume of the loan portfolio and in the terms of loans
| o | Changes in the experience, ability and depth of lending management and other relevant staff
| o | Changes in the volume and severity of past due loans, nonaccrual loans and adversely classified loans
| o | Changes in the quality of the loan review program
| o | Changes in the value of underlying collateral dependent loans
| o | Existence and effect of any concentrations of credit and any changes in such
| o | Effect of other factors such as competition and legal and regulatory requirements
| o | Local or regional conditions that depart from the conditions and forecasts for the entire country
The estimation of future credit losses should reflect consideration of all significant factors that affect the collectibility of the loan portfolio at each evaluation date. While our methodology considers both the historical loss rates as well as the traditional qualitative factors, there may be instances or situations where additional qualitative factors need to be considered. Effective January 1, 2022, we established a historical loss information factor to address the relatively low level of loan losses during the look-back period. Accrued interest receivable on loans totaling $16.9 million and $12.8 million as of December 31, 2023 and 2022, respectively, is included in other assets on the Consolidated Balance Sheets. We elected not to measure an allowance for accrued interest receivable and instead elected to reverse interest income on loans that are placed on nonaccrual status, which is generally when the loan becomes 90 days past due, or earlier if we believe the collection of interest is doubtful. We believe this policy results in the timely reversal of uncollectible interest. Identified problem loans, which exhibit characteristics (financial or otherwise) that could cause the loans to become nonperforming or require restructuring in the future, are included on an internal watch list. Senior management and the Board of Directors review this list regularly. In some cases, we may determine that an individual loan exhibits unique risk characteristics which differentiate the loan from other loans within the loan segments. In such cases, the loans are evaluated for expected credit losses on an individual basis and excluded from the collective evaluation. Specific reserve allocations of the allowance for credit losses are determined by analyzing the borrower’s ability to repay amounts owed, and collateral deficiencies, among other things. For individually analyzed loans which are deemed to be collateral dependent loans, we adopted the practical expedient to measure the allowance based on the fair value of collateral. The allowance is calculated on an individual loan basis based on the shortfall between the fair value of the loan’s collateral and the recorded principal balance. If the fair value of the collateral exceeds the recorded principal balance, no allowance is required. Fair value estimates of collateral on individually analyzed loans, as well as on foreclosed and repossessed assets, are reviewed periodically. We also have a process in place to monitor whether value estimates at each quarter-end are reflective of current market conditions. Our credit policies establish criteria for obtaining appraisals and determining internal value estimates. We may also adjust outside and internal valuations based on identifiable trends within our markets, such as recent sales of similar properties or assets, listing prices and offers received. In addition, we may discount certain appraised and internal value estimates to address distressed market conditions. We are also required to consider expected credit losses associated with loan commitments over the contractual period in which we are exposed to credit risk on the underlying commitments unless the obligation is unconditionally cancellable by us. Any allowance for off-balance sheet credit exposures is reported as an other liability on our Consolidated Balance Sheets and is increased or decreased via other noninterest expense on our Consolidated Statement of Income. The calculation includes consideration of the likelihood that funding will occur and forecasted credit losses on commitments expected to be funded over their estimated lives. The allowance is calculated using the same aggregate reserve rates calculated for the funded portion of loans at the portfolio level applied to the amount of commitments expected to be funded.
Transfers and Servicing of Financial Assets, Policy [Policy Text Block] | Transfers of Financial Assets: Transfers of financial assets are accounted for as sales when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when: (1) the assets have been isolated from our bank and put presumptively beyond the reach of the transferor and its creditors, even in bankruptcy or other receivership, (2) the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets, and (3) our bank does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity or the ability to unilaterally cause the holder to return specific assets. Our transfers of financial assets are generally limited to commercial loan participations sold and residential mortgage loans sold in the secondary market.
Property, Plant and Equipment, Policy [Policy Text Block] | Premises and Equipment: Land is carried at cost. Premises and equipment are stated at cost less accumulated depreciation. Buildings and related components are depreciated using the straight-line method with useful lives ranging from 5 to 33 years. Furniture, fixtures and equipment are depreciated using the straight-line method with useful lives ranging from 3 to 7 years. Maintenance, repairs and minor alterations are charged to current operations as expenditures occur and major improvements are capitalized. Premises and equipment are reviewed for impairment when events indicate their carrying amount may not be recoverable based on future undiscounted cash flows. If impaired, the assets are recorded at the lower of carrying value or fair value.
Financing Receivable, Held-for-Investment, Foreclosed Asset [Policy Text Block] | Foreclosed Assets: Assets acquired through or in lieu of foreclosure are initially recorded at their estimated fair value net of estimated selling costs, establishing a new cost basis. If fair value subsequently declines, a valuation allowance is recorded through noninterest expense, as are collection and operating costs after acquisition. Foreclosed assets, included in other assets in the Consolidated Balance Sheets, totaled $0.2 million and $0 as of December 31, 2023 and 2022, respectively.
Bank Owned Life Insurance, Policy [Policy Text Block] | Bank Owned Life Insurance: Our bank has purchased life insurance policies on certain key officers. Bank owned life insurance is recorded at its cash surrender value, or the amount that can be realized. Increases in the net cash surrender value of the policies, as well as insurance proceeds received, are recorded as noninterest income on the Consolidated Statements of Income and are not subject to income taxes.
Goodwill and Intangible Assets, Policy [Policy Text Block] | Goodwill: The acquisition method of accounting requires that assets and liabilities acquired in a business combination are recorded at fair value as of the acquisition date. The valuation of assets and liabilities often involves estimates based on third-party valuations or internal valuations based on discounted cash flow analyses or other valuation techniques, all of which are inherently subjective. This typically results in goodwill, the amount by which the cost of net assets acquired in a business combination exceeds their fair value, which is subject to impairment testing at least annually. We review goodwill for impairment on an annual basis as of October 1 or more often if events or circumstances indicate that it is more-likely-than-not that the fair value of a reporting unit is below its carrying value. Based on our annual impairment analysis of goodwill as of October 1, it was determined that the fair value was in excess of its respective carrying value as of October 1, 2023; therefore, goodwill is considered not impaired.
Repurchase and Resale Agreements Policy [Policy Text Block] | Repurchase Agreements: Our bank sells certain securities under agreements to repurchase. The agreements are treated as collateralized financing transactions, with the obligations to repurchase the securities sold reflected as liabilities and the securities underlying the agreements remaining in assets in the Consolidated Balance Sheets.
Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block] | Financial Instruments and Loan Commitments: Financial instruments include off-balance-sheet credit instruments, such as commitments to make loans and commercial letters of credit, issued to meet customer financing needs. The face amount for these items represents the exposure to loss, before considering customer collateral or ability to repay. Such financial instruments are recorded when they are funded. Instruments, such as standby letters of credit, that are considered financial guarantees are recorded at fair value. Reserves for unfunded commitments are recorded as an other liability on our Consolidated Balance Sheets.
Share-Based Payment Arrangement [Policy Text Block] | Stock-Based Compensation: Compensation cost for equity-based awards is measured on the grant date based on the fair value of the award at that date, and is recognized over the requisite service period, net of estimated forfeitures. Fair value of stock option awards is estimated using a closed option valuation (Black-Scholes) model. Fair value of restricted stock awards is based upon the quoted market price of the common stock on the date of grant.
Revenue from Contract with Customer [Policy Text Block] | Revenue from Contracts with Customers: We record revenue from contracts with customers in accordance with Accounting Standards Codification Topic 606, “Revenue from Contracts with Customers” (“Topic 606”). Under Topic 606, we must identify the contract with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) we satisfy a performance obligation. Significant revenue has not been recognized in the current reporting period that results from performance obligations satisfied in previous periods. Our primary sources of revenue are derived from interest and dividends earned on loans, securities and other financial instruments that are not within the scope of Topic 606. We have evaluated the nature of our contracts with customers and determined that further disaggregation of revenue from contracts with customers into more granular categories beyond what is presented in the Consolidated Statements of Income was not necessary. We generally satisfy our performance obligations on contracts with customers as services are rendered, and the transaction prices are typically fixed and charged either on a periodic basis (generally monthly) or based on activity. Because performance obligations are satisfied as services are rendered and the transaction prices are fixed, there is little judgment involved in applying Topic 606 that significantly affects the determination of the amount and timing of revenue from contracts with customers. The following table depicts our sources of noninterest income presented in the Consolidated Statements of Income for the years ended December 31, 2023, 2022 and 2021 that are scoped within Topic 606:
(Dollars in thousands) |  | 2023 |  |  | 2022 |  |  | 2021 |
Service charges on deposit and sweep accounts |  | $ | 4,954 |  |  | $ | 5,952 |  |  | $ | 5,078 |
Credit and debit card fees |  |  | 8,914 |  |  |  | 8,216 |  |  |  | 7,516 |
Payroll processing |  |  | 2,509 |  |  |  | 2,178 |  |  |  | 1,815 |
Customer service fees |  |  | 801 |  |  |  | 852 |  |  |  | 857 |
Service Charges on Deposit and Sweep Accounts: We earn fees from deposit and sweep customers for account maintenance, transaction-based and overdraft services. Account maintenance fees, which relate primarily to monthly maintenance, are earned over the course of the month reflecting the period over which we satisfy the performance obligation. Transaction-based fees, which includes services such as stop payment and returned item charges, are recognized at the time the transaction is executed as that is the point in time we fulfill the customer request. Service charges on deposit and sweep accounts are withdrawn from the customer account balance. Credit and Debit Card Fees: We earn interchange income on our cardholder debit and credit card usage. Interchange income is primarily comprised of fees whenever our debit and credit cards are processed through card payment networks such as Visa. Interchange fees from cardholder transactions represent a percentage of the underlying transaction value and are recognized daily, concurrently with the transaction processing services provided to the cardholder. Payroll Processing Fees: We earn fees from providing payroll processing services for our commercial clients. Fees are assessed for processing weekly or bi-weekly payroll files, reports and documents, as well as year-end tax-related files, reports and documents. Fees are recognized and collected as payroll processing services are completed for each payroll run and year-end processing activities. Customer Service Fees: We earn fees by providing a variety of other services to our customers, such as wire transfers, check ordering, sales of cashier checks and money orders, and rentals of safe deposit boxes. Generally, fees are recognized and collected daily, concurrently with the point in time we fulfill the customer request. Safe deposit box rentals are on annual contracts, with fees generally earned at the time of the contract signing or renewal. Customer service fees are recorded as other noninterest income on our Consolidated Statements of Income.
Advertising Cost [Policy Text Block] | Advertising Costs: Advertising costs are expensed as incurred.
Income Tax, Policy [Policy Text Block] | Income Taxes: Income tax expense is the total of the current year income tax due or refundable, the change in deferred income tax assets and liabilities, and any adjustments related to unrecognized tax benefits. Deferred income tax assets and liabilities are recognized for the tax consequences of temporary differences between the carrying amounts and tax bases of assets and liabilities, computed using enacted tax rates applicable to future years. A valuation allowance, if needed, reduces deferred income tax assets to the amount expected to be realized.
Fair Value of Financial Instruments, Policy [Policy Text Block] | Fair Values of Financial Instruments: Fair values of financial instruments are estimated using relevant market information and other assumptions. Fair value estimates involve uncertainties and matters of significant judgment regarding interest rates, credit risk, prepayments and other factors, especially in the absence of broad markets for particular items. Changes in assumptions or in market conditions could significantly affect the estimates. The fair value estimates of existing on- and off-balance sheet financial instruments do not include the value of anticipated future business or the values of assets and liabilities not considered financial instruments.
Earnings Per Share, Policy [Policy Text Block] | Earnings Per Share: Basic earnings per share is based on the weighted average number of common shares and participating securities outstanding during the period. Diluted earnings per share include the dilutive effect of additional potential common shares issuable under our stock-based compensation plans using the treasury stock method. Our unvested stock awards, which contain non-forfeitable rights to dividends whether paid or unpaid (i.e., participating securities), are included in the number of shares outstanding for both basic and diluted earnings per share calculations. In the event of a net loss, our unvested stock awards are excluded from the calculations of both basic and diluted earnings per share.
Comprehensive Income, Policy [Policy Text Block] | Comprehensive Income (Loss): Comprehensive income (loss) consists of net income and other comprehensive income (loss). Accumulated other comprehensive gain/(loss) includes unrealized gains and losses on securities available for sale. Accumulated other comprehensive gain/(loss) was comprised of the following as of December 31, 2023, 2022, and 2021:
(Dollars in thousands) |  | 2023 |  |  | 2022 |  |  | 2021 |
Unrealized gains (losses) on securities available for sale |  | $ | (63,906 | ) |  | $ | (82,710 | ) |  | $ | (4,720 | )
Tax effect |  |  | 13,419 |  |  |  | 17,369 |  |  |  | 991 |
Accumulated other comprehensive gain/(loss) |  | $ | (50,487 | ) |  | $ | (65,341 | ) |  | $ | (3,729 | )
Derivatives, Policy [Policy Text Block] | Derivatives: Derivative financial instruments are recognized as assets or liabilities at fair value. The accounting for changes in the fair value of derivatives depends on the use of the derivatives and whether the derivatives qualify for hedge accounting. Used as part of our asset and liability management to help manage interest rate risk, our derivatives have historically generally consisted of interest rate swap agreements that qualified for hedge accounting. We do not use derivatives for trading purposes. Changes in the fair value of derivatives that are designated, for accounting purposes, as a hedge of the variability of cash flows to be received on various assets and liabilities and are effective are reported in other comprehensive income. They are later reclassified into earnings in the same periods during which the hedged transaction affects earnings and are included in the line item in which the hedged cash flows are recorded. If hedge accounting does not apply, changes in the fair value of derivatives are recognized immediately in current earnings as interest income or expense. We had no derivative instruments designated as hedges as of December 31, 2023 and 2022.
Commitments and Contingencies, Policy [Policy Text Block] | Contingencies: Loss contingencies, including claims and legal actions arising in the ordinary course of business, are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated. We do not believe there are any such matters outstanding that would have a material effect on the financial statements
New Accounting Pronouncements, Policy [Policy Text Block] | Recent Accounting Changes Adopted: ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments. This ASU (as subsequently amended by ASU 2018-19) significantly changed how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. This standard replaced the “incurred loss” approach with an “expected loss” model. Referred to as the current expected credit loss (“CECL”) model, this standard applies to financial assets subject to credit losses and measured at amortized cost, and certain off-balance sheet credit exposures. The standard also expanded disclosure requirements regarding an entity’s assumptions, models, and methods for estimating the allowance. In addition, entities need to disclose the amortized cost balance for each class of financial asset by credit quality indicator, disaggregated by the year of origination. We adopted CECL effective January 1, 2022 using the modified retrospective method for all financial assets measured at amortized cost and off-balance sheet credit exposures. Results for reporting periods beginning after January 1, 2022 are presented under CECL while prior period amounts continue to be reported in accordance with the incurred loss accounting standards. The transition adjustment of the CECL adoption included a decrease in the allowance of $0.4 million, and a $0.3 million increase to the retained earnings account to reflect the cumulative effect of adopting CECL on our Consolidated Balance Sheet, with the $0.1 million tax impact portion being recorded as part of the deferred tax asset in other assets on our Consolidated Balance Sheet. ASU No. 2022-02, Troubled Debt Restructurings and Vintage Disclosures. This ASU eliminated the accounting guidance for troubled debt restructurings (“TDRs”) by creditors in Subtopic 310-40, Receivables – Troubled Debt Restructurings by Creditors, while adding disclosures for certain loan restructurings by creditors when a borrower is experiencing financial difficulty. This guidance requires an entity to determine whether the modification results in a new loan or a continuation of an existing loan. Additionally, the ASU requires disclosures of current period gross charge-offs by year of origination for financing receivables. This ASU is effective for fiscal years beginning after December 15, 2022. We have adopted the standard and included the required disclosures in our financial statements. ASU 2023-02 Accounting for Investments in Tax Credit Structures Using the Proportional Amortization Method. This ASU permits reporting entities to elect to account for their tax equity investments, regardless of the tax credit program from which the income tax credits are received, using the proportional amortization if certain conditions are met. A reporting entity makes an accounting policy election to apply the proportional amortization method on a tax-credit-by-tax-credit-program basis rather than electing to apply the proportional amortization method at the reporting entity level or to individual investments. Mercantile adopted the standard using a modified retrospective transition approach to the amendments related to our low-income housing tax credit ("LIHTC") investments that are eligible to apply proportional amortization, which were previously accounted for under the equity method. The cumulative effect to retained earnings as of January 1, 2023 was immaterial. Our proportionate share of losses in the underlying investments recorded in our Consolidated Statements of Income in other expense during the years ended December 31, 2022 and 2021 was $0.3 million and $0.2 million, respectively. During the year ended December 31, 2023, we recognized $0.5 million of proportional amortization expense recorded in our Consolidated Statements of Income in federal income tax expense. See Note 18, Variable Interest Entities, for further details on our investments in tax credit entities.

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