Summary of Significant Accounting Policies	12 Months Ended
Dec. 31, 2011
Summary of Significant Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 1 - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Principles of Consolidation: The consolidated financial statements include the accounts of Mercantile Bank Corporation (“Mercantile”) and its subsidiary, Mercantile Bank of Michigan (“Bank”), and of Mercantile Bank Mortgage Company, LLC (“Mortgage Company”), Mercantile Bank Real Estate Co., L.L.C. (“Mercantile Real Estate”) and Mercantile Insurance Center, Inc. (“Mercantile Insurance”), subsidiaries of our Bank, after elimination of significant intercompany transactions and accounts. We formed a business trust, Mercantile Bank Capital Trust I (“our trust”), in 2004 to issue trust preferred securities. We issued subordinated debentures to our trust in return for the proceeds raised from the issuance of the trust preferred securities. In accordance with accounting guidelines, our trust is not consolidated, but instead we report the subordinated debentures issued to the trust as a liability. Nature of Operations: Mercantile was incorporated on July 15, 1997 to establish and own the Bank based in Grand Rapids, Michigan. The Bank is a community-based financial institution, and began operations on December 15, 1997. The 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. The Bank’s loan accounts and retail deposits are primarily with customers located in the Grand Rapids, Holland and Lansing areas. As an alternative source of funds, the 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. Mercantile Bank Mortgage Company was formed during 2000. A subsidiary of the Bank, Mercantile Bank Mortgage Company was established to increase the profitability and efficiency of the mortgage loan operations. Mercantile Bank Mortgage Company initiated business on October 24, 2000 via the Bank’s contribution of most of its residential mortgage loan portfolio and participation interests in certain commercial mortgage loans. On the same date, the Bank also transferred its residential mortgage origination function to Mercantile Bank Mortgage Company. On January 1, 2004, Mercantile Bank Mortgage Company was reorganized as the Mortgage Company, a limited liability company, which is 99% owned by the Bank and 1% owned by Mercantile Insurance. Mortgage loans originated and held by the Mortgage Company are serviced by the Bank pursuant to a servicing agreement. Mercantile Insurance was formed during 2002 through the acquisition of an existing shelf insurance agency. Insurance products are offered through an Agency and Institutions Agreement among Mercantile Insurance, the Bank and Hub International. The insurance products are marketed through a central facility operated by the Michigan Bankers Insurance Association, members of which include the insurance subsidiaries of various Michigan-based financial institutions and Hub International. Mercantile Insurance receives commissions based upon written premiums produced under the Agency and Institutions Agreement. Mercantile Real Estate was organized on July 21, 2003, principally to develop, construct, and own a facility in downtown Grand Rapids that serves as our Bank’s main office and Mercantile’s headquarters. This facility was placed into service during the second quarter of 2005. 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 loan losses and the fair values of financial instruments are particularly subject to change. Cash Flow Reporting: Cash and cash equivalents include cash on hand, demand deposits with other financial institutions, short-term investments (including securities with daily put provisions) and federal funds sold. Cash flows are reported net for customer loan and deposit transactions, interest-bearing time deposits with other financial institutions and short-term borrowings with maturities of 90 days or less. 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 are classified as available for sale when they might be sold prior to maturity. Equity securities with readily determinable fair values are classified as available for sale. Securities available for sale are carried at fair value, with unrealized holding gains and losses reported in other comprehensive income, net of tax (as applicable). Other securities such as FHLB stock are carried at cost. 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. Declines in the fair value of securities below their amortized cost that are other than temporary are reflected in earnings or other comprehensive income, as appropriate. For those debt securities whose fair value is less than their amortized cost basis, we consider our intent to sell the security, whether it is more likely than not that we will be required to sell the security before recovery and if we do not expect to recover the entire amortized cost basis of the security. In analyzing an issuer’s financial condition, we may consider whether the securities are issued by the federal government or its agencies, whether downgrades by bond rating agencies have occurred and the results of reviews of the issuer’s financial condition. Loans: Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at the principal balance outstanding, net of deferred loan fees and costs and an allowance for loan losses. 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 fees amounted to $0.4 million and $0.5 million at December 31, 2011 and 2010, 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. Loans Held for Sale: Mortgage loans originated and intended for sale in the secondary market are carried at the lower of aggregate cost or market, as determined by outstanding commitments from investors. Net unrealized losses, if any, are recorded as a valuation allowance and charged to earnings. Such loans are sold service released. The balance of loans held for sale equaled $2.6 million and $2.7 million as of December 31, 2011 and 2010, respectively. Mortgage banking activities include fees on direct brokered mortgage loans and the net gain on sale of mortgage loans originated for sale. Troubled Debt Restructurings: A loan is accounted for as a troubled debt restructuring if we, for economic or legal reasons, grant a concession to a borrower considered to be experiencing financial difficulties that we would not otherwise consider. A troubled debt restructuring may involve 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 can be in either accrual or nonaccrual status. Nonaccrual troubled debt restructurings are included in nonperforming loans. Accruing troubled debt restructurings are generally excluded from nonperforming loans as it is considered probable that all contractual principal and interest due under the restructured terms will be collected. In accordance with current accounting guidance, loans modified as troubled debt restructurings are, by definition, considered to be impaired loans. Impairment for these loans is measured on a loan-by-loan basis similar to other impaired loans as described below under “Allowance for Loan Losses.” 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 will be impacted by the difference between the results of these two measurement methodologies. Loans modified as troubled debt restructurings that subsequently default are factored in to the determination of the allowance for loan losses in the same manner as other defaulted loans. Allowance for Loan Losses: The allowance for loan losses (“allowance”) is a valuation allowance for probable incurred credit losses. Loan losses are charged against the allowance when we believe the uncollectability of a loan is confirmed. Subsequent recoveries, if any, are credited to the allowance. We estimate the allowance balance required using past loan loss experience, the nature and volume of the loan portfolio, information about specific borrower situations and estimated collateral values, economic conditions and other factors. Allocations of the allowance may be made for specific loans, but the entire allowance is available for any loan that, in our judgment, should be charged-off. A loan is considered impaired when, based on current information and events, it is probable we will be unable to collect the scheduled payments of principal and interest when due according to the contractual terms of the loan agreement. Factors considered in determining impairment include payment status, collateral value and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. We determine the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of delay, the reasons for delay, the borrower’s prior payment record and the amount of the shortfall in relation to the principal and interest owed. Impairment is measured on a loan-by-loan basis for commercial and construction loans by the present value of expected future cash flows discounted at the loan’s effective interest rate, the loan’s obtainable market price or the fair value of collateral if the loan is collateral dependent. Large groups of smaller balance homogeneous loans are collectively evaluated for impairment. We do not separately identify individual residential and consumer loans for impairment disclosures. 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 the 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) the 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 limited to commercial loan participations sold, which were insignificant for 2011, 2010 and 2009, the 2010 sale of the guaranteed portions of certain Small Business Administration-guaranteed loans, the 2010 sale of tax-exempt municipal bonds and the sale of residential mortgage loans in the secondary market; the extent of the latter three are disclosed in the Consolidated Statements of Cash Flows. 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. Long-lived Assets: Premises and equipment and other long-lived assets are reviewed for impairment when events indicate their carrying amount may not be recoverable from future undiscounted cash flows. If impaired, the assets are recorded at the lower of carrying value or fair value. Foreclosed Assets: Assets acquired through or in lieu of foreclosure are initially recorded at the estimated fair value net of estimated selling costs when acquired, establishing a new cost basis. If fair value declines, a valuation allowance is recorded through noninterest expense, as are collection and operating costs after acquisition. Bank Owned Life Insurance: The 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. Repurchase Agreements: The Bank sells certain securities under agreements to repurchase. The agreements are treated as collateralized financing transactions, and the obligations to repurchase securities sold are reflected as a liability in the Consolidated Balance Sheet. The dollar amount of the securities underlying the agreements remains in the asset accounts. 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. 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. 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. At December 31, 2011, we reversed the full valuation allowance that was initially recorded at December 31, 2009, as described in Note 8. 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: 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 and our common stock warrant, and are determined 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 (Loss): Comprehensive income (loss) consists of net income (loss) and other comprehensive income (loss). Other comprehensive income includes unrealized gains and losses on securities available for sale which are also recognized as separate components of equity. For 2010 and 2009, other comprehensive income (loss) also includes the change in fair value of interest rate swaps, and the reclassification of unrealized gain on the interest rate swaps. 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 consisted of interest rate swap agreements that qualified for hedge accounting. In June 2011, as discussed in more detail in Note 13, we simultaneously purchased and sold an interest rate cap, a structure commonly referred to as a “cap corridor”, which does not qualify for hedge accounting. We had no derivatives outstanding during 2010 or 2009. 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. If designated as a hedge, we formally document the relationship between derivatives as hedged items, as well as the risk-management objective and the strategy for undertaking hedge transactions. This documentation includes linking cash flow hedges to specific assets on the balance sheet. If designated as a hedge, we also formally assess, both at the hedge’s inception and on an ongoing basis, whether the derivative instruments that are used are highly effective in offsetting changes in cash flows of the hedged items. Ineffective hedge gains and losses are recognized immediately in current earnings as noninterest income or expense. We discontinue hedge accounting when we determine the derivative is no longer effective in offsetting changes in the cash flows of the hedged item, the derivative is settled or terminates, or treatment of the derivatives as a hedge is no longer appropriate or intended. 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 that would have a material effect on the financial statements. Operating Segment: While we monitor the revenue streams of the various products and services offered, Mercantile manages its business on the basis of one operating segment, banking. Adoption of New Accounting Standards: In January 2010, the Financial Accounting Standards Board (“FASB”) issued ASU 2010-06, Improving Disclosure about Fair Value Measurements. This ASU requires new disclosures on the amount and reason for transfers in and out of Level 1 and Level 2 recurring fair value measurements. The ASU also requires disclosure of activities (i.e., on a gross basis), including purchases, sales, issuances, and settlements, in the reconciliation of Level 3 fair value recurring measurements. The ASU clarifies existing disclosure requirements on levels of disaggregation and disclosures about inputs and valuation techniques. The new disclosure regarding Level 1 and Level 2 fair value measurements and clarification of existing disclosures are effective for periods beginning January 1, 2010. Upon adoption of those portions of the ASU in our 2010 first quarter, we began providing the required disclosures as currently presented in Note 15. The disclosures about the reconciliation of information in Level 3 recurring fair value measurements were required for periods beginning January 1, 2011. There was no effect on our fair value disclosures presented in Note 15 upon the adoption of the final portion of the ASU in our 2011 first quarter, as we currently have no Level 3 recurring fair value measurements. In July 2010, the FASB issued ASU 2010-20, Disclosures about the Credit Quality of Financing Receivables and the Allowance for Credit Losses. In order to provide greater transparency, this ASU requires significant new disclosures on a disaggregated basis about the allowance for credit losses (e.g., allowance for banks) and the credit quality of financing receivables (e.g., loans for banks). Under the ASU, a rollforward schedule of the allowance, with the ending allowance balance further disaggregated on the basis of the impairment method, along with the related ending loan balance and significant purchases and sales of loans during the period are to be disclosed by portfolio segment. Additional disclosures are required by class of loan, including credit quality, aging of past due loans, nonaccrual status and impairment information. Disclosure of the nature and extent of troubled debt restructurings that occurred during the period and their effect on the allowance as well as the effect on the allowance of troubled debt restructurings that occurred within the prior twelve months that defaulted during the current reporting period will also be required. The disclosures are to be presented at the level of disaggregation that management uses when assessing and monitoring the loan portfolio’s risk and performance. The majority of the disclosures required as of the end of a reporting period were effective as of December 31, 2010. Upon adoption of those portions of the ASU on December 31, 2010, we began providing the required end of period disclosures as currently presented in Note 3. The disclosures about activity were effective January 1, 2011. Upon adoption of the final portion of the ASU in our 2011 first quarter, we began providing the required activity disclosures, with the exception of the new troubled debt restructuring related disclosures, as currently presented in Note 3. In January 2011, the FASB issued ASU 2011-01, Deferral of the Effective Date of Disclosures about Troubled Debt Restructurings in Update No. 2010-20, which temporarily deferred the effective date for disclosures related to troubled debt restructurings. As discussed in the next paragraph, beginning with the 2011 third quarter, we began providing the required troubled debt disclosures as presented in Note 3. In April 2011, the FASB issued ASU 2011-02, A Creditor’s Determination of Whether a Restructuring is a Troubled Debt Restructuring, to clarify when a loan modification or restructuring is considered a TDR. When performing this evaluation under the ASU, a creditor must use judgment to determine whether (1) the debtor (i.e., the borrower) is experiencing financial difficulty, and (2) the lender has granted a concession to the borrower. The ASU amends current guidance to include indicators that a lender should consider in determining whether a borrower is experiencing financial difficulties. It further clarifies that a borrower could be experiencing financial difficulty even if it is not currently in default but default is probable in the foreseeable future. With respect to whether the lender has granted a concession to the borrower, the ASU indicates (1) a borrower’s inability to access funds at a market interest rate for debt with similar risk characteristics as the restructured debt indicates that the modification was executed at a below-market rate and therefore may indicate a concession was granted, (2) a modification that permanently or temporarily increases a loan’s contractual interest rate does not preclude it from being considered a concession because the rate may still be below the market interest rate for new debt with similar risk characteristics, and (3) a modification that results in a delay in payment that is insignificant is not considered to be a concession. The ASU also clarifies that a creditor is precluded from using the borrower’s effective interest rate test when performing this evaluation. For TDR identification and disclosure purposes, the guidance became effective for our 2011 third quarter and was applied retrospectively to modifications occurring on or after January 1, 2011 that remained outstanding at September 30, 2011. The effect of the change in the method of calculating impairment was reflected in our 2011 third quarter. As required by the ASU, we disclosed in our 2011 third quarter Form 10-Q the total recorded investment and allowance for loan losses for newly identified TDRs, based on the new guidance, as of September 30, 2011. Beginning in our 2011 third quarter Form 10-Q, we also disclosed the previously deferred TDR activity related disclosures required by ASU 2010-20 in Note 3. In April 2011, the FASB issued ASU 2011-03, Reconsideration of Effective Control for Repurchase Agreements, to improve financial reporting of repurchase agreements and other agreements that both entitle and obligate a transferor to repurchase or redeem financial assets on substantially the agreed upon terms. This ASU eliminates consideration of the transferor’s ability to fulfill its contractual rights and obligations from the criteria, as well as related implementation guidance (i.e., that it possesses adequate collateral to fund substantially all the cost of purchasing replacement financial assets), in determining effective control, even in the event of default by the transferee. Other criteria applicable to the assessment of effective control are not changed by this new guidance. This ASU is effective January 1, 2012. We do not expect the adoption of this new ASU to have a material effect on our results of operations or financial position. In May 2011, the FASB issued ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS, to align the fair value measurement and disclosure requirements in U.S. GAAP and International Financial Reporting Standards (“IFRSs”). Many of the amendments in this ASU will not result in a change in requirements but simply clarify existing requirements. The amendments in this ASU that do not change a principle or requirement for measuring fair value or disclosing information about fair value measurements include the following: (1) the ASU permits an exception for measuring fair value when a reporting entity manages its financial instruments on the basis of its net exposure, rather than gross exposure, to those risks; (2) the ASU clarifies that the application of premiums and discounts in a fair value measurement is related to the unit of account for the asset or liability being measured at fair value and specifically prohibits blockage discounts for Level 2 and 3 investments; and (3) the amendments expand fair value measurement disclosures. The more significant new disclosures include: (1) for all Level 3 fair value measurements, quantitative information about significant unobservable inputs used as well as a qualitative discussion about the sensitivity of recurring Level 3 fair value measurements; (2) transfers between Level 1 and Level 2 fair value measurements on a gross basis, including the reasons for those transfers; and (3) the categorization by level of the fair value hierarchy for items that are not measured at fair value in the balance sheet but for which the fair value is required to be disclosed (e.g., held-to-maturity securities and loans). The ASU is to be applied prospectively and is effective January 1, 2012. We do not expect the adoption of this new ASU to have a material effect on our results of operations or financial position. In June 2011, the FASB issued ASU 2011-05, Presentation of Comprehensive Income, to improve the comparability, consistency and transparency of financial reporting and to increase the prominence of items reported in other comprehensive income. The ASU eliminates the option to present components of other comprehensive income as part of the Statement of Changes in Shareholders’ Equity. Instead, all components of comprehensive income must be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. In the single continuous statement approach, the statement should present the components of net income and total net income, the components of other comprehensive income and total other comprehensive income, and a total for comprehensive income. In the two-statement approach, the first statement should present the components of net income and total net income followed consecutively by a second statement that should present the components of other comprehensive income, a total for other comprehensive income and a total for comprehensive income. Also known as “recycling,” companies will also be required to display reclassification adjustments and their effect on net income and other comprehensive income in the statement(s) in which they appear. The ASU does not change certain other current requirements including items that constitute net income and other comprehensive income. The ASU is to be applied retrospectively and is effective January 1, 2012. We are currently evaluating the two presentation approaches permitted by the ASU. In December 2011, the FASB issued ASU 2011-12, Deferral of the Effective Date for Amendments to the Presentation of Reclassification of Items Out of Accumulated Other Comprehensive Income in Update No. 2011-05, which defers indefinitely the ASU 2011-05 requirement that entities disclose on the face of the financial statements reclassification adjustments for items that are reclassified from other comprehensive income to net income.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1 - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Principles of Consolidation: The consolidated financial statements include the accounts of Mercantile Bank Corporation (“Mercantile”) and its subsidiary, Mercantile Bank of Michigan (“Bank”), and of Mercantile Bank Mortgage Company, LLC (“Mortgage Company”), Mercantile Bank Real Estate Co., L.L.C. (“Mercantile Real Estate”) and Mercantile Insurance Center, Inc. (“Mercantile Insurance”), subsidiaries of our Bank, after elimination of significant intercompany transactions and accounts.

We formed a business trust, Mercantile Bank Capital Trust I (“our trust”), in 2004 to issue trust preferred securities. We issued subordinated debentures to our trust in return for the proceeds raised from the issuance of the trust preferred securities. In accordance with accounting guidelines, our trust is not consolidated, but instead we report the subordinated debentures issued to the trust as a liability.

Nature of Operations: Mercantile was incorporated on July 15, 1997 to establish and own the Bank based in Grand Rapids, Michigan. The Bank is a community-based financial institution, and began operations on December 15, 1997. The 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. The Bank’s loan accounts and retail deposits are primarily with customers located in the Grand Rapids, Holland and Lansing areas. As an alternative source of funds, the 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.

Mercantile Bank Mortgage Company was formed during 2000. A subsidiary of the Bank, Mercantile Bank Mortgage Company was established to increase the profitability and efficiency of the mortgage loan operations. Mercantile Bank Mortgage Company initiated business on October 24, 2000 via the Bank’s contribution of most of its residential mortgage loan portfolio and participation interests in certain commercial mortgage loans. On the same date, the Bank also transferred its residential mortgage origination function to Mercantile Bank Mortgage Company. On January 1, 2004, Mercantile Bank Mortgage Company was reorganized as the Mortgage Company, a limited liability company, which is 99% owned by the Bank and 1% owned by Mercantile Insurance. Mortgage loans originated and held by the Mortgage Company are serviced by the Bank pursuant to a servicing agreement.

Mercantile Insurance was formed during 2002 through the acquisition of an existing shelf insurance agency. Insurance products are offered through an Agency and Institutions Agreement among Mercantile Insurance, the Bank and Hub International. The insurance products are marketed through a central facility operated by the Michigan Bankers Insurance Association, members of which include the insurance subsidiaries of various Michigan-based financial institutions and Hub International. Mercantile Insurance receives commissions based upon written premiums produced under the Agency and Institutions Agreement.

Mercantile Real Estate was organized on July 21, 2003, principally to develop, construct, and own a facility in downtown Grand Rapids that serves as our Bank’s main office and Mercantile’s headquarters. This facility was placed into service during the second quarter of 2005.

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 loan losses and the fair values of financial instruments are particularly subject to change.

Cash Flow Reporting: Cash and cash equivalents include cash on hand, demand deposits with other financial institutions, short-term investments (including securities with daily put provisions) and federal funds sold. Cash flows are reported net for customer loan and deposit transactions, interest-bearing time deposits with other financial institutions and short-term borrowings with maturities of 90 days or less.

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 are classified as available for sale when they might be sold prior to maturity. Equity securities with readily determinable fair values are classified as available for sale. Securities available for sale are carried at fair value, with unrealized holding gains and losses reported in other comprehensive income, net of tax (as applicable). Other securities such as FHLB stock are carried at cost.

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.

Declines in the fair value of securities below their amortized cost that are other than temporary are reflected in earnings or other comprehensive income, as appropriate. For those debt securities whose fair value is less than their amortized cost basis, we consider our intent to sell the security, whether it is more likely than not that we will be required to sell the security before recovery and if we do not expect to recover the entire amortized cost basis of the security. In analyzing an issuer’s financial condition, we may consider whether the securities are issued by the federal government or its agencies, whether downgrades by bond rating agencies have occurred and the results of reviews of the issuer’s financial condition.

Loans: Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at the principal balance outstanding, net of deferred loan fees and costs and an allowance for loan losses. 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 fees amounted to $0.4 million and $0.5 million at December 31, 2011 and 2010, 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.

Loans Held for Sale: Mortgage loans originated and intended for sale in the secondary market are carried at the lower of aggregate cost or market, as determined by outstanding commitments from investors. Net unrealized losses, if any, are recorded as a valuation allowance and charged to earnings. Such loans are sold service released. The balance of loans held for sale equaled $2.6 million and $2.7 million as of December 31, 2011 and 2010, respectively. Mortgage banking activities include fees on direct brokered mortgage loans and the net gain on sale of mortgage loans originated for sale.

Troubled Debt Restructurings: A loan is accounted for as a troubled debt restructuring if we, for economic or legal reasons, grant a concession to a borrower considered to be experiencing financial difficulties that we would not otherwise consider. A troubled debt restructuring may involve 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 can be in either accrual or nonaccrual status. Nonaccrual troubled debt restructurings are included in nonperforming loans. Accruing troubled debt restructurings are generally excluded from nonperforming loans as it is considered probable that all contractual principal and interest due under the restructured terms will be collected.

In accordance with current accounting guidance, loans modified as troubled debt restructurings are, by definition, considered to be impaired loans. Impairment for these loans is measured on a loan-by-loan basis similar to other impaired loans as described below under “Allowance for Loan Losses.” 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 will be impacted by the difference between the results of these two measurement methodologies. Loans modified as troubled debt restructurings that subsequently default are factored in to the determination of the allowance for loan losses in the same manner as other defaulted loans.

Allowance for Loan Losses: The allowance for loan losses (“allowance”) is a valuation allowance for probable incurred credit losses. Loan losses are charged against the allowance when we believe the uncollectability of a loan is confirmed. Subsequent recoveries, if any, are credited to the allowance. We estimate the allowance balance required using past loan loss experience, the nature and volume of the loan portfolio, information about specific borrower situations and estimated collateral values, economic conditions and other factors. Allocations of the allowance may be made for specific loans, but the entire allowance is available for any loan that, in our judgment, should be charged-off.

A loan is considered impaired when, based on current information and events, it is probable we will be unable to collect the scheduled payments of principal and interest when due according to the contractual terms of the loan agreement. Factors considered in determining impairment include payment status, collateral value and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. We determine the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of delay, the reasons for delay, the borrower’s prior payment record and the amount of the shortfall in relation to the principal and interest owed. Impairment is measured on a loan-by-loan basis for commercial and construction loans by the present value of expected future cash flows discounted at the loan’s effective interest rate, the loan’s obtainable market price or the fair value of collateral if the loan is collateral dependent. Large groups of smaller balance homogeneous loans are collectively evaluated for impairment. We do not separately identify individual residential and consumer loans for impairment disclosures.

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 the 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) the 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 limited to commercial loan participations sold, which were insignificant for 2011, 2010 and 2009, the 2010 sale of the guaranteed portions of certain Small Business Administration-guaranteed loans, the 2010 sale of tax-exempt municipal bonds and the sale of residential mortgage loans in the secondary market; the extent of the latter three are disclosed in the Consolidated Statements of Cash Flows.

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.

Long-lived Assets: Premises and equipment and other long-lived assets are reviewed for impairment when events indicate their carrying amount may not be recoverable from future undiscounted cash flows. If impaired, the assets are recorded at the lower of carrying value or fair value.

Foreclosed Assets: Assets acquired through or in lieu of foreclosure are initially recorded at the estimated fair value net of estimated selling costs when acquired, establishing a new cost basis. If fair value declines, a valuation allowance is recorded through noninterest expense, as are collection and operating costs after acquisition.

Bank Owned Life Insurance: The 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.

Repurchase Agreements: The Bank sells certain securities under agreements to repurchase. The agreements are treated as collateralized financing transactions, and the obligations to repurchase securities sold are reflected as a liability in the Consolidated Balance Sheet. The dollar amount of the securities underlying the agreements remains in the asset accounts.

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.

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.

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. At December 31, 2011, we reversed the full valuation allowance that was initially recorded at December 31, 2009, as described in Note 8.

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: 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 and our common stock warrant, and are determined 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 (Loss): Comprehensive income (loss) consists of net income (loss) and other comprehensive income (loss). Other comprehensive income includes unrealized gains and losses on securities available for sale which are also recognized as separate components of equity. For 2010 and 2009, other comprehensive income (loss) also includes the change in fair value of interest rate swaps, and the reclassification of unrealized gain on the interest rate swaps.

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 consisted of interest rate swap agreements that qualified for hedge accounting. In June 2011, as discussed in more detail in Note 13, we simultaneously purchased and sold an interest rate cap, a structure commonly referred to as a “cap corridor”, which does not qualify for hedge accounting. We had no derivatives outstanding during 2010 or 2009. 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.

If designated as a hedge, we formally document the relationship between derivatives as hedged items, as well as the risk-management objective and the strategy for undertaking hedge transactions. This documentation includes linking cash flow hedges to specific assets on the balance sheet. If designated as a hedge, we also formally assess, both at the hedge’s inception and on an ongoing basis, whether the derivative instruments that are used are highly effective in offsetting changes in cash flows of the hedged items. Ineffective hedge gains and losses are recognized immediately in current earnings as noninterest income or expense. We discontinue hedge accounting when we determine the derivative is no longer effective in offsetting changes in the cash flows of the hedged item, the derivative is settled or terminates, or treatment of the derivatives as a hedge is no longer appropriate or intended.

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 that would have a material effect on the financial statements.

Operating Segment: While we monitor the revenue streams of the various products and services offered, Mercantile manages its business on the basis of one operating segment, banking.

Adoption of New Accounting Standards: In January 2010, the Financial Accounting Standards Board (“FASB”) issued ASU 2010-06, Improving Disclosure about Fair Value Measurements. This ASU requires new disclosures on the amount and reason for transfers in and out of Level 1 and Level 2 recurring fair value measurements. The ASU also requires disclosure of activities (i.e., on a gross basis), including purchases, sales, issuances, and settlements, in the reconciliation of Level 3 fair value recurring measurements. The ASU clarifies existing disclosure requirements on levels of disaggregation and disclosures about inputs and valuation techniques. The new disclosure regarding Level 1 and Level 2 fair value measurements and clarification of existing disclosures are effective for periods beginning January 1, 2010. Upon adoption of those portions of the ASU in our 2010 first quarter, we began providing the required disclosures as currently presented in Note 15. The disclosures about the reconciliation of information in Level 3 recurring fair value measurements were required for periods beginning January 1, 2011. There was no effect on our fair value disclosures presented in Note 15 upon the adoption of the final portion of the ASU in our 2011 first quarter, as we currently have no Level 3 recurring fair value measurements.

In July 2010, the FASB issued ASU 2010-20, Disclosures about the Credit Quality of Financing Receivables and the Allowance for Credit Losses. In order to provide greater transparency, this ASU requires significant new disclosures on a disaggregated basis about the allowance for credit losses (e.g., allowance for banks) and the credit quality of financing receivables (e.g., loans for banks). Under the ASU, a rollforward schedule of the allowance, with the ending allowance balance further disaggregated on the basis of the impairment method, along with the related ending loan balance and significant purchases and sales of loans during the period are to be disclosed by portfolio segment. Additional disclosures are required by class of loan, including credit quality, aging of past due loans, nonaccrual status and impairment information. Disclosure of the nature and extent of troubled debt restructurings that occurred during the period and their effect on the allowance as well as the effect on the allowance of troubled debt restructurings that occurred within the prior twelve months that defaulted during the current reporting period will also be required. The disclosures are to be presented at the level of disaggregation that management uses when assessing and monitoring the loan portfolio’s risk and performance. The majority of the disclosures required as of the end of a reporting period were effective as of December 31, 2010. Upon adoption of those portions of the ASU on December 31, 2010, we began providing the required end of period disclosures as currently presented in Note 3. The disclosures about activity were effective January 1, 2011. Upon adoption of the final portion of the ASU in our 2011 first quarter, we began providing the required activity disclosures, with the exception of the new troubled debt restructuring related disclosures, as currently presented in Note 3. In January 2011, the FASB issued ASU 2011-01, Deferral of the Effective Date of Disclosures about Troubled Debt Restructurings in Update No. 2010-20, which temporarily deferred the effective date for disclosures related to troubled debt restructurings. As discussed in the next paragraph, beginning with the 2011 third quarter, we began providing the required troubled debt disclosures as presented in Note 3.

In April 2011, the FASB issued ASU 2011-02, A Creditor’s Determination of Whether a Restructuring is a Troubled Debt Restructuring, to clarify when a loan modification or restructuring is considered a TDR. When performing this evaluation under the ASU, a creditor must use judgment to determine whether (1) the debtor (i.e., the borrower) is experiencing financial difficulty, and (2) the lender has granted a concession to the borrower. The ASU amends current guidance to include indicators that a lender should consider in determining whether a borrower is experiencing financial difficulties. It further clarifies that a borrower could be experiencing financial difficulty even if it is not currently in default but default is probable in the foreseeable future. With respect to whether the lender has granted a concession to the borrower, the ASU indicates (1) a borrower’s inability to access funds at a market interest rate for debt with similar risk characteristics as the restructured debt indicates that the modification was executed at a below-market rate and therefore may indicate a concession was granted, (2) a modification that permanently or temporarily increases a loan’s contractual interest rate does not preclude it from being considered a concession because the rate may still be below the market interest rate for new debt with similar risk characteristics, and (3) a modification that results in a delay in payment that is insignificant is not considered to be a concession. The ASU also clarifies that a creditor is precluded from using the borrower’s effective interest rate test when performing this evaluation. For TDR identification and disclosure purposes, the guidance became effective for our 2011 third quarter and was applied retrospectively to modifications occurring on or after January 1, 2011 that remained outstanding at September 30, 2011. The effect of the change in the method of calculating impairment was reflected in our 2011 third quarter. As required by the ASU, we disclosed in our 2011 third quarter Form 10-Q the total recorded investment and allowance for loan losses for newly identified TDRs, based on the new guidance, as of September 30, 2011. Beginning in our 2011 third quarter Form 10-Q, we also disclosed the previously deferred TDR activity related disclosures required by ASU 2010-20 in Note 3.

In April 2011, the FASB issued ASU 2011-03, Reconsideration of Effective Control for Repurchase Agreements, to improve financial reporting of repurchase agreements and other agreements that both entitle and obligate a transferor to repurchase or redeem financial assets on substantially the agreed upon terms. This ASU eliminates consideration of the transferor’s ability to fulfill its contractual rights and obligations from the criteria, as well as related implementation guidance (i.e., that it possesses adequate collateral to fund substantially all the cost of purchasing replacement financial assets), in determining effective control, even in the event of default by the transferee. Other criteria applicable to the assessment of effective control are not changed by this new guidance. This ASU is effective January 1, 2012. We do not expect the adoption of this new ASU to have a material effect on our results of operations or financial position.

In May 2011, the FASB issued ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS, to align the fair value measurement and disclosure requirements in U.S. GAAP and International Financial Reporting Standards (“IFRSs”). Many of the amendments in this ASU will not result in a change in requirements but simply clarify existing requirements. The amendments in this ASU that do not change a principle or requirement for measuring fair value or disclosing information about fair value measurements include the following: (1) the ASU permits an exception for measuring fair value when a reporting entity manages its financial instruments on the basis of its net exposure, rather than gross exposure, to those risks; (2) the ASU clarifies that the application of premiums and discounts in a fair value measurement is related to the unit of account for the asset or liability being measured at fair value and specifically prohibits blockage discounts for Level 2 and 3 investments; and (3) the amendments expand fair value measurement disclosures. The more significant new disclosures include: (1) for all Level 3 fair value measurements, quantitative information about significant unobservable inputs used as well as a qualitative discussion about the sensitivity of recurring Level 3 fair value measurements; (2) transfers between Level 1 and Level 2 fair value measurements on a gross basis, including the reasons for those transfers; and (3) the categorization by level of the fair value hierarchy for items that are not measured at fair value in the balance sheet but for which the fair value is required to be disclosed (e.g., held-to-maturity securities and loans). The ASU is to be applied prospectively and is effective January 1, 2012. We do not expect the adoption of this new ASU to have a material effect on our results of operations or financial position.

In June 2011, the FASB issued ASU 2011-05, Presentation of Comprehensive Income, to improve the comparability, consistency and transparency of financial reporting and to increase the prominence of items reported in other comprehensive income. The ASU eliminates the option to present components of other comprehensive income as part of the Statement of Changes in Shareholders’ Equity. Instead, all components of comprehensive income must be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. In the single continuous statement approach, the statement should present the components of net income and total net income, the components of other comprehensive income and total other comprehensive income, and a total for comprehensive income. In the two-statement approach, the first statement should present the components of net income and total net income followed consecutively by a second statement that should present the components of other comprehensive income, a total for other comprehensive income and a total for comprehensive income. Also known as “recycling,” companies will also be required to display reclassification adjustments and their effect on net income and other comprehensive income in the statement(s) in which they appear. The ASU does not change certain other current requirements including items that constitute net income and other comprehensive income. The ASU is to be applied retrospectively and is effective January 1, 2012. We are currently evaluating the two presentation approaches permitted by the ASU. In December 2011, the FASB issued ASU 2011-12, Deferral of the Effective Date for Amendments to the Presentation of Reclassification of Items Out of Accumulated Other Comprehensive Income in Update No. 2011-05, which defers indefinitely the ASU 2011-05 requirement that entities disclose on the face of the financial statements reclassification adjustments for items that are reclassified from other comprehensive income to net income.

- Definition

The entire disclosure for all significant accounting policies of the reporting entity.

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