SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
Dec. 31, 2013
Accounting Policies [Abstract]
Principles of Consolidation	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	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 Mercantile Bank Mortgage Company, LLC, a limited liability company, which was 99% owned by the Bank and 1% owned by Mercantile Insurance. Mortgage loans originated and held by the mortgage company were serviced by the Bank pursuant to a servicing agreement. Effective January 1, 2013, we dissolved the mortgage company to streamline the administration of our mortgage business. A cash amount commensurate with its 1% ownership interest was distributed to the insurance company. The remaining assets of the mortgage company were assigned to the Bank. We anticipate the business that was formerly conducted by the mortgage company to be performed by the Bank in its ordinary course and do not expect the dissolution to materially impact our financial position or results of operation. 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	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 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	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). FHLB stock is 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 debt 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, 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 whether we expect to recover the entire amortized cost of the security based on our assessment of the issuer’s financial condition. In analyzing an issuer’s financial condition, we consider whether the securities are issued by the federal government or its agencies, and whether downgrades by bond rating agencies have occurred. If either of the criteria regarding intent or requirement to sell is met, the entire difference between amortized cost and fair value is recognized as impairment through earnings. For debt securities that do not meet the aforementioned criteria, the amount of impairment is split into two components as follows: 1) OTTI related to credit loss, which must be recognized in the income statement, and 2) OTTI related to other factors, such as liquidity conditions in the market or changes in market interest rates, which is recognized in other comprehensive income. The credit loss is defined as the difference between the present value of the cash flows expected to be collected and the amortized cost.
Loans	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 $0.5 million and $0.7 million at December 31, 2013 and 2012, 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	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. Such loans are sold servicing released. Loans held for sale amounted to $1.1 million and $3.5 million as of December 31, 2013 and 2012, respectively. Income from mortgage banking activities includes fees on direct brokered mortgage loans and the net gain on sale of mortgage loans originated for sale.
Troubled Debt Restructurings	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. 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	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. We estimate credit losses based on individual loans determined to be impaired and on all other loans grouped on similar risk characteristics. Our historical loss component is the most significant of the allowance components and is based on historical loss experience by credit risk grade for commercial loans and payment status for mortgage and consumer loans. Loans are pooled based on similar risk characteristics supported by observable data. The historical loss experience component of the allowance represents the results of migration analysis of historical net charge-offs for portfolios of loans, including groups of commercial loans within each credit risk grade. For measuring loss exposure in a pool of loans, the historical net charge-off or migration experience is utilized to estimate expected future losses to be realized from the pool of loans. 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 and collateral value. 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.
Transfers of Financial Assets	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 generally limited to commercial loan participations sold and residential mortgage loans originated for sale, which were insignificant for 2013, 2012 and 2011.
Premises and Equipment	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	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 based on future undiscounted cash flows. If impaired, the assets are recorded at the lower of carrying value or fair value.
Foreclosed Assets	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.
Bank Owned Life Insurance	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	Repurchase Agreements: The 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 Sheet.
Financial Instruments and Loan Commitments	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	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 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: 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	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 granted to the U.S. Department of Treasury that we repurchased on July 3, 2012, 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	Comprehensive Income: Comprehensive income consists of net income and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized gains and losses on securities available for sale and interest rate swaps which are also recognized as separate components of equity.
Derivatives	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 February 2012, we entered into an interest rate swap agreement that qualifies for hedge accounting. However, in June 2011, 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. The current outstanding interest rate swap agreement and matured cap corridor are discussed in more detail in Note 13. 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 the derivative instrument and the hedged item, as well as the risk-management objective and the strategy for undertaking the hedge transaction. 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 instrument that is used is 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	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.
Operating Segment	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	Adoption of New Accounting Standards: In February 2013, the FASB issued ASU 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, which is intended to improve the reporting of reclassifications out of accumulated other comprehensive income. The ASU requires an entity to report, either on the face of the income statement or in the notes to the financial statements, the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in the income statement. We adopted this ASU in the first quarter of 2013.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2013

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

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 Mercantile Bank Mortgage Company, LLC, a limited liability company, which was 99% owned by the Bank and 1% owned by Mercantile Insurance. Mortgage loans originated and held by the mortgage company were serviced by the Bank pursuant to a servicing agreement. Effective January 1, 2013, we dissolved the mortgage company to streamline the administration of our mortgage business. A cash amount commensurate with its 1% ownership interest was distributed to the insurance company. The remaining assets of the mortgage company were assigned to the Bank. We anticipate the business that was formerly conducted by the mortgage company to be performed by the Bank in its ordinary course and do not expect the dissolution to materially impact our financial position or results of operation.

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

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 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

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). FHLB stock is 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 debt 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, 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 whether we expect to recover the entire amortized cost of the security based on our assessment of the issuer’s financial condition. In analyzing an issuer’s financial condition, we consider whether the securities are issued by the federal government or its agencies, and whether downgrades by bond rating agencies have occurred. If either of the criteria regarding intent or requirement to sell is met, the entire difference between amortized cost and fair value is recognized as impairment through earnings. For debt securities that do not meet the aforementioned criteria, the amount of impairment is split into two components as follows: 1) OTTI related to credit loss, which must be recognized in the income statement, and 2) OTTI related to other factors, such as liquidity conditions in the market or changes in market interest rates, which is recognized in other comprehensive income. The credit loss is defined as the difference between the present value of the cash flows expected to be collected and the amortized cost.

Loans

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 $0.5 million and $0.7 million at December 31, 2013 and 2012, 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

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. Such loans are sold servicing released. Loans held for sale amounted to $1.1 million and $3.5 million as of December 31, 2013 and 2012, respectively. Income from mortgage banking activities includes fees on direct brokered mortgage loans and the net gain on sale of mortgage loans originated for sale.

Troubled Debt Restructurings

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.

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

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. We estimate credit losses based on individual loans determined to be impaired and on all other loans grouped on similar risk characteristics. Our historical loss component is the most significant of the allowance components and is based on historical loss experience by credit risk grade for commercial loans and payment status for mortgage and consumer loans. Loans are pooled based on similar risk characteristics supported by observable data. The historical loss experience component of the allowance represents the results of migration analysis of historical net charge-offs for portfolios of loans, including groups of commercial loans within each credit risk grade. For measuring loss exposure in a pool of loans, the historical net charge-off or migration experience is utilized to estimate expected future losses to be realized from the pool of loans. 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 and collateral value. 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.

Transfers of Financial Assets

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 generally limited to commercial loan participations sold and residential mortgage loans originated for sale, which were insignificant for 2013, 2012 and 2011.

Premises and Equipment

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

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 based on future undiscounted cash flows. If impaired, the assets are recorded at the lower of carrying value or fair value.

Foreclosed Assets

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.

Bank Owned Life Insurance

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

Repurchase Agreements: The 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 Sheet.

Financial Instruments and Loan Commitments

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

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 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: 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

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 granted to the U.S. Department of Treasury that we repurchased on July 3, 2012, 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

Comprehensive Income: Comprehensive income consists of net income and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized gains and losses on securities available for sale and interest rate swaps which are also recognized as separate components of equity.

Derivatives

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 February 2012, we entered into an interest rate swap agreement that qualifies for hedge accounting. However, in June 2011, 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. The current outstanding interest rate swap agreement and matured cap corridor are discussed in more detail in Note 13. 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 the derivative instrument and the hedged item, as well as the risk-management objective and the strategy for undertaking the hedge transaction. 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 instrument that is used is 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

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.

Operating Segment

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

Adoption of New Accounting Standards: In February 2013, the FASB issued ASU 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, which is intended to improve the reporting of reclassifications out of accumulated other comprehensive income. The ASU requires an entity to report, either on the face of the income statement or in the notes to the financial statements, the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in the income statement. We adopted this ASU in the first quarter of 2013.