Summary of Significant Accounting Policies	12 Months Ended
Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES The significant accounting policies used by the Company in the preparation of the consolidated financial statements are summarized below. Business and Consolidation Enterprise Financial Services Corp and subsidiaries (the “Company” or “Enterprise”) is a financial holding company that provides a full range of banking and wealth management services to individuals and corporate customers primarily located in the St. Louis, Kansas City, and Phoenix metropolitan markets through its banking subsidiary, Enterprise Bank & Trust (the “Bank”). The consolidated financial statements include the accounts of the Company, and its subsidiaries, all of which are wholly owned. All intercompany accounts and transactions have been eliminated. The Company is subject to competition from other financial and nonfinancial institutions providing financial services in the markets served by the Company's subsidiary. Additionally, the Company and its banking subsidiary are subject to the regulations of certain federal and state agencies and undergo periodic examinations by those regulatory agencies. The Company has one operating segment. Use of Estimates The consolidated financial statements of the Company have been prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”). In preparing the consolidated financial statements, management is required to make estimates and assumptions, which significantly affect the reported amounts in the consolidated financial statements. Such estimates include the valuation of loans, goodwill, intangible assets, indemnification assets, and other long-lived assets, along with assumptions used in the calculation of income taxes, among others. These estimates and assumptions are based on management's best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using experience and other factors, including the current economic environment, which management believes to be reasonable under the circumstances. Management adjusts such estimates and assumptions when facts and circumstances dictate. Decreased real estate values, volatile credit markets, and unemployment have combined to increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in those estimates resulting from continuing changes in the economic environment will be reflected in the financial statements in future periods. Cash Flow Information For purposes of reporting cash flows, the Company considers cash and due from banks, interest-bearing deposits and federal funds sold that mature within 90 days of the balance sheet date to be cash and cash equivalents. At December 31, 2017 and 2016, approximately $17.5 million, and $18.2 million, respectively, of cash and due from banks represented required reserves on deposits maintained by the Company in accordance with Federal Reserve Bank requirements. Investments The Company has classified all investments in debt securities as available for sale or held to maturity. Securities classified as available for sale are carried at fair value. Unrealized holding gains and losses for available for sale securities are excluded from earnings and reported as a net amount in a separate component of shareholders' equity until realized. All previous fair value adjustments included in the separate component of shareholders' equity are reversed upon sale. Securities classified as held to maturity are carried at historical cost and adjusted for amortization of premiums and accretion of discounts. Declines in the fair value of securities below their cost deemed to be other-than-temporary are reflected in operations as realized losses. In estimating other-than-temporary impairment losses, management systematically evaluates investment securities for other-than-temporary declines in fair value on a quarterly basis. This analysis requires management to consider various factors, which include (1) the present value of the cash flows expected to be collected compared to the amortized cost of the security, (2) duration and magnitude of the decline in value, (3) the financial condition of the issuer or issuers, (4) structure of the security, and (5) the intent to sell the security or whether it's more likely than not the Company would be required to sell the security before its anticipated recovery in market value. Premiums and discounts are amortized or accreted over the expected lives of the respective securities as an adjustment to yield using the interest method. Dividend and interest income is recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold. Loans Held for Sale The Company provides long-term financing of one-to-four-family residential real estate by originating fixed and variable rate loans. Long-term fixed and variable rate loans are sold into the secondary market with limited recourse. Upon receipt of an application for a real estate loan, the Company determines whether the loan will be sold into the secondary market or retained in the Company's loan portfolio. The interest rates on the loans sold are locked with the buyer and the Company bears no interest rate risk related to these loans. Mortgage loans held for sale are carried at the lower of cost or fair value, which is determined on a specific identification method. The Company does not retain servicing on any loans sold, nor did the Company have any capitalized mortgage servicing rights at December 31, 2017 or 2016. Gains on the sale of loans held for sale are reported net of direct origination fees and costs in the Company's consolidated statements of operations. Portfolio Loans Loans are reported at the principal balance outstanding, net of unearned fees, costs, and premiums or discounts on acquired loans. Loan origination fees, direct origination costs, and premiums or discounts resulting from acquired loans are deferred and recognized over the lives of the related loans as a yield adjustment using the interest method. Interest income on loans is accrued to income based on the principal amount outstanding. The recognition of interest income is discontinued when a loan becomes 90 days past due or a significant deterioration in the borrower's credit has occurred which, in management's judgment, negatively impacts the collectibility of the loan. Unpaid interest on such loans is reversed at the time the loan becomes uncollectible and subsequent interest payments received are applied to principal if any doubt exists as to the collectibility of such principal; otherwise, such receipts are recorded as interest income. Loans that have not been restructured are returned to accrual status when management believes full collectibility of principal and interest is expected. Non-accrual loans that have been restructured will remain in a non-accrual status until the borrower has made at least six months of consecutive contractual payments. Purchased Credit Impaired ("PCI") Loans PCI loans were acquired in a business combination or transaction, that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments receivable. PCI loans were initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance. The difference between the undiscounted cash flows expected at acquisition and the investment in the loans, or the “accretable yield,” is recognized as interest income on a level-yield method over the life of the loans. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “nonaccretable difference,” are not recognized as a yield adjustment or as a loss accrual or a valuation allowance. The Company aggregates individual loans with common risk characteristics into pools of loans. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loans over their remaining lives. Decreases in expected cash flows due to an inability to collect contractual cash flows are recognized as impairment through the provision for loan losses account. Any allowance for loan loss on these pools reflect only losses incurred after the acquisition. Disposals of loans, including sales of loans, paydowns, payments in full or foreclosures result in the removal or reduction of the loan from the loan pool. PCI loans are generally considered accruing and performing, as the loans accrete income over the estimated life of the loan, in circumstances where cash flows are reasonably estimable by management. Accordingly, PCI loans that could be contractually past due could be considered to be accruing and performing. If the timing and amount of future cash flows is not reasonably estimable or is less than the carrying value, the loans may be classified as nonaccrual loans and the purchase price discount on those loans is not recorded as interest income until the timing and amount of future cash flows can be reasonably estimable. Impaired Loans Loans are considered “impaired” when it becomes probable that the Company will be unable to collect all amounts due according to the loan's contractual terms. Non-accrual loans, loans past due greater than 90 days and still accruing, unless adequately secured and in the process of collection, and restructured loans qualify as “impaired loans.” Restructured loans involve the granting of a concession to a borrower experiencing financial difficulty involving the modification of terms of the loan, such as changes in payment schedule or interest rate. When measuring impairment, the expected future cash flows of an impaired loan are discounted at the loan's effective interest rate at origination. Alternatively, impairment can be measured by reference to an observable market price, if one exists, or the fair value of the collateral for a collateral-dependent loan. Interest income on impaired loans is not accrued but is recorded when cash is received and only if principal is considered to be fully collectible. Loans and leases, which are deemed uncollectible, are charged off to the allowance for loan losses, while recoveries of amounts previously charged off are credited to the allowance for loan losses. Impaired loans exclude PCI loans, as described above. Although, if the timing and amount of future cash flows is not reasonably estimable, the loans may be classified as nonaccrual loans and the purchase price discount on those loans is not recorded as interest income until the timing and amount of future cash flows can be reasonably estimated. See Note 5 – Loans for more information on these loans. Loans are generally placed on non-accrual status when contractually past due 90 days or more as to interest or principal payments. Additionally, whenever management becomes aware of facts or circumstances that may adversely impact the collectability of principal or interest on loans, it is management's practice to place such loans on non-accrual status immediately, rather than delaying such action until the loans become 90 days past due. Previously accrued and uncollected interest on such loans is reversed. Income is recorded only to the extent that a determination has been made that the principal balance of the loan is collectable and the interest payments are subsequently received in cash, or for a restructured loan, the borrower has made six consecutive contractual payments. If collectability of the principal is in doubt, payments received are applied to loan principal. Loans past due 90 days or more but still accruing interest are also generally included in nonperforming loans. Loans past due 90 days or more but still accruing are classified as such where the underlying loans are both well secured (the collateral value is sufficient to cover principal and accrued interest) and are in the process of collection. At December 31, 2017, we did not have any loans past due greater than 90 days and not included in nonperforming loans. Loan Charge-Offs Loans are charged-off when the primary and secondary sources of repayment (cash flow, collateral, guarantors, etc.) are less than their carrying value. Allowance For Loan Losses The allowance for loan losses is increased by provision charged to expense and is available to absorb charge-offs, net of recoveries. Management utilizes a systematic, documented approach in determining the appropriate level of the allowance for loan losses. The level of the allowance reflects management's continuing evaluation of industry concentrations; specific credit risks; loan loss experience; current loan portfolio quality; present economic, political and regulatory conditions; and probable losses inherent in the current loan portfolio. The determination of the appropriate level of the allowance for loan losses inherently involves a degree of subjectivity and requires that the Company make significant estimates of current credit risks and future trends, all of which may undergo material changes. Changes in economic conditions affecting borrowers, new information regarding existing loans, identification of additional problem loans and other factors, both within and outside of our control, may require an increase in the allowance for loan losses. Management believes the allowance for loan losses is adequate to absorb inherent losses in the loan portfolio. While management uses available information to recognize losses on loans, future additions to the allowance may be necessary based on changes in economic conditions and other factors. In addition, various regulatory agencies, as an integral part of the examination process, periodically review the Bank's loan portfolio. Such agencies may require additions to the allowance for loan losses based on their judgments and interpretations of information available to them at the time of their examinations. Allowance for Loan Losses on PCI Loans The Company updates its cash flow projections for PCI loans on a periodic basis. Assumptions utilized in this process include projections related to probability of default, loss severity, prepayment, extensions and recovery lag. Projections related to probability of default and prepayment are calculated utilizing a loan migration analysis and management's assessment of loss exposure including the fair value of underlying collateral. The loan migration analysis is a matrix that specifies the probability of a loan pool transitioning into a particular delinquency or liquidation state given its current performance at the measurement date. Loss severity factors are based upon industry data and historical experience. Any decreases in expected cash flows after the acquisition date and subsequent measurement periods are recognized by recording an impairment in allowance for loan losses. Other Real Estate Other real estate represents property acquired through foreclosure or deeded to the Company in lieu of foreclosure on loans on which the borrowers have defaulted on the payment of principal or interest. Other real estate is recorded on an individual asset basis at the lower of cost or fair value less estimated costs to sell. The fair value of other real estate is based upon estimates of future cash flows, market value of similar assets, if available, or independent appraisals. These estimates involve significant uncertainties and judgments. As a result, fair value estimates may not be realizable in a current sale or settlement of the other real estate. Subsequent reductions in fair value are expensed within noninterest expense. Gains and losses resulting from the sale of other real estate are credited or charged to current period earnings. Costs of maintaining and operating other real estate are expensed as incurred, and expenditures to complete or improve other real estate properties are capitalized if the expenditures are expected to be recovered upon ultimate sale of the property. Fixed Assets Buildings, leasehold improvements, furniture, fixtures, equipment, and capitalized software are stated at cost less accumulated depreciation. All categories are computed using the straight-line method over their respective estimated useful lives. Furniture, fixtures and equipment is depreciated over three to ten years, buildings and leasehold improvements over ten to forty years, and capitalized software over three years based upon estimated lives or lease obligation periods. State Tax Credits Held for Sale The Company has purchased the rights to receive 10-year streams of state tax credits at agreed upon discount rates and sells such tax credits to its clients and others. All state tax credits purchased prior to 2009 are accounted for at fair value. All state tax credits purchased since 2009 are accounted for at cost. The Company elected not to account for the state tax credits purchased since 2009 at fair value in order to limit the volatility of the fair value changes in the Company's consolidated statements of operations. Cash Surrender Value of Life Insurance The Company has purchased bank-owned life insurance policies on certain bank officers. Bank-owned life insurance is recorded at its cash surrender value. Changes in the cash surrender values are included in noninterest income. Federal Home Loan Bank Stock The Bank, as a member of the Federal Home Loan Bank of Des Moines (“FHLB”), is required to maintain an investment in the capital stock of the FHLB. The stock is redeemable at par by the FHLB, and is, therefore, carried at cost and periodically evaluated for impairment. The Company records FHLB dividends in interest income. Goodwill and Other Intangible Assets The Company tests goodwill for impairment on an annual basis and whenever events or changes in circumstances indicate that the Company may not be able to recover the respective asset's carrying amount. The Company's annual test for impairment was performed in the fourth quarter of December 31, 2017. Such tests involve the use of estimates and assumptions. Core deposit intangibles are amortized using an accelerated method over an estimated useful life of approximately 10 years. Potential impairments to goodwill must first be identified by performing a qualitative assessment which evaluates relevant events or circumstances to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If this test indicates it is more likely than not that goodwill has been impaired, then a quantitative impairment test is completed. The quantitative impairment test calculates the fair value of the reporting unit and compares it with its carrying amount, including goodwill. If the carrying amount of goodwill exceeds its implied fair market value, an impairment loss is recognized. That loss is equal to the carrying amount of goodwill that is in excess of its implied fair market value. Impairment of Long-Lived Assets Long-lived assets, such as fixed assets and purchased intangibles subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets to be disposed of are separately presented in the balance sheet and reported at the lower of the carrying amount or fair value less costs to sell, and are no longer depreciated. The assets and liabilities of a disposal group classified as held for sale are presented separately in the appropriate asset and liability sections of the balance sheet. Derivative Financial Instruments and Hedging Activities The Company uses derivative financial instruments to assist in the management of interest rate sensitivity and to modify the repricing, maturity and option characteristics of certain assets and liabilities. In addition, the Company also offers an interest rate hedge program that includes interest rate swaps to assist its customers in managing their interest rate risk profile. In order to eliminate the interest rate risk associated with offering these products, the Company enters into derivative contracts with third parties to offset the customer contracts. Derivative instruments are required to be measured at fair value and recognized as either assets or liabilities in the consolidated financial statements. Fair value represents the payment the Company would receive or pay if the item were sold or bought in a current transaction. The accounting for changes in fair value (gains or losses) of a hedged item is dependent on whether the related derivative is designated and qualifies for “hedge accounting.” The Company assigns derivatives to one of these categories at the purchase date: cash flow hedge, fair value hedge, or non-designated derivatives. An assessment of the expected and ongoing hedge effectiveness of any derivative designated a fair value hedge or cash flow hedge is performed as required by the accounting standards. Derivatives are included in other assets and other liabilities in the consolidated balance sheets. Generally, the only derivative instruments used by the Company have been interest rate swaps and interest rate caps. The Company does not currently have derivative instruments designated as fair value or cash flow hedges. Certain derivative financial instruments are not designated as cash flow or as fair value hedges for accounting purposes. These non-designated derivatives are intended to provide interest rate protection on net interest income or noninterest income but do not meet hedge accounting treatment. Customer accommodation interest rate swap contracts are not designated as hedging instruments. Changes in the fair value of these instruments are recorded in interest income or noninterest income in the consolidated statements of income depending on the underlying hedged item. Income Taxes The Company and its subsidiaries file a consolidated federal income tax return. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. We evaluated the need for deferred tax asset valuation allowances based on a more-likely-than-not standard. The ability to realize deferred tax assets depends on the ability to generate sufficient positive taxable income within the carryback or carryforward periods provided for in the laws for each applicable taxing jurisdiction. We consider the following possible sources of taxable income: future reversal patterns of existing taxable temporary differences, future taxable income exclusive of reversing temporary differences, taxable income in prior carryback years and the availability of qualified tax planning strategies. The assessment regarding whether a valuation allowance is required or should be adjusted depends on all available positive and negative factors including, but not limited to, nature, frequency, and severity of recent losses, duration of available carryforward periods, experience with tax attributes expiring unused and near and medium term financial outlook. Because of the complexity of tax laws and regulations, interpretation can be difficult and subject to legal judgment given specific facts and circumstances. It is possible that others, given the same information, may at any point in time reach different reasonable conclusions regarding the estimated amounts of accrued taxes. The SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Cuts and Jobs Act of 2017 (“Tax Act”). SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. The Company has recorded amounts based on the information known and reasonable estimates used as of December 31, 2017, but are subject to change based on a number of factors. The Company will complete its analysis of certain tax positions at the time it files its tax returns for the year ended December 31, 2017 and will be able to conclude if any further adjustments to the provisional estimate of the impact recorded is required. Stock-Based Compensation Stock-based compensation is recognized as an expense for stock options, restricted stock awards, and restricted stock units granted to employees in return for employee service. Equity classified awards are measured at the grant date fair value using either an observable market value or a valuation methodology, and recognized over the requisite service period on a straight-line basis. Forfeitures are recorded as they occur. A description of the Company's stock-based employee compensation plan is described in Note 15 - Compensation Plans. Acquisitions and Divestitures Acquisitions and business combinations are accounted for using the acquisition method of accounting. The assets and liabilities of the acquired entities have been recorded at their estimated fair values at the date of acquisition. Goodwill represents the excess of the purchase price over the fair value of net assets acquired, including the amount assigned to identifiable intangible assets. The purchase price allocation process requires an estimation of the fair values of the assets acquired and the liabilities assumed. When a business combination agreement provides for an adjustment to the cost of the combination contingent on future events, the Company includes an estimate of the acquisition-date fair value as part of the cost of the combination. To determine the fair values, the Company relies on third party valuations, such as appraisals, or internal valuations based on discounted cash flow analyses or other valuation techniques. The results of operations of the acquired business are included in the Company's consolidated financial statements from the date of acquisition. Merger-related costs are costs the Company incurs to effect a business combination. In 2017, the Company changed its presentation of Merger related expenses as a separate component of Noninterest expenses on the Condensed Consolidated Statements of Operations. Merger related expenses include costs directly related to merger or acquisition activity and include legal and professional fees, system consolidation and conversion costs, and compensation costs such as severance and retention incentives for employees impacted by acquisition activity. The Company accounts for merger-related costs as expenses in the periods in which the costs are incurred and the services are received. For divestitures, the Company measures an asset (disposal group) classified as held for sale at the lower of its carrying value at the date the asset is initially classified as held for sale or its fair value less costs to sell. The Company reports the results of operations of an entity or group of components that either has been disposed of or held for sale as discontinued operations only if the disposal of that component represents a strategic shift that has or will have a major effect on an entity's operations and financial results. Any incremental direct costs incurred to transact the sale are allocated against the gain or loss on the sale. These costs would include items like legal fees, title transfer fees, broker fees, etc. Any goodwill and intangible assets associated with the portion of the reporting unit to be disposed of is included in the carrying amount of the business in determining the gain or loss on the sale. Basic and Diluted Earnings Per Common Share Basic earnings per common share data is calculated by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. Common shares outstanding include common stock and restricted stock awards where recipients have satisfied the vesting terms. Diluted earnings per common share gives effect to all dilutive potential common shares outstanding during the period using the treasury stock method. Consolidated Statement of Comprehensive Income The Consolidated Statement of Comprehensive Income includes the amount and the related tax impact that have been reclassified from accumulated other comprehensive income to net income. The classification adjustment for unrealized loss/gain on sale of securities included in net income has been recorded through the gain on sale of investment securities line item, within noninterest income, in the Company's Consolidated Statements of Operations. Reclassifications Some items in the prior year financial statements were reclassified to conform to the current presentation. In 2017, the Company changed its presentation of loans on the face of the Consolidated Balance Sheets to combine originated loans with purchased loans. See Note 5 - Loans for more information. The Company also changed its presentation of the Noninterest Income section on the face of the Consolidated Statements of Operations to separate card services revenue from other service charges and fee income. The difference was reclassified into miscellaneous income. Merger related expenses were reclassified from other expenses to be a separate component of the Noninterest Expense section on the Consolidated Statements of Operations. Reclassifications had no effect on prior year net income or shareholders' equity.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

The significant accounting policies used by the Company in the preparation of the consolidated financial statements are summarized below.

Business and Consolidation

Enterprise Financial Services Corp and subsidiaries (the “Company” or “Enterprise”) is a financial holding company that provides a full range of banking and wealth management services to individuals and corporate customers primarily located in the St. Louis, Kansas City, and Phoenix metropolitan markets through its banking subsidiary, Enterprise Bank & Trust (the “Bank”). The consolidated financial statements include the accounts of the Company, and its subsidiaries, all of which are wholly owned. All intercompany accounts and transactions have been eliminated.

The Company is subject to competition from other financial and nonfinancial institutions providing financial services in the markets served by the Company's subsidiary. Additionally, the Company and its banking subsidiary are subject to the regulations of certain federal and state agencies and undergo periodic examinations by those regulatory agencies. The Company has one operating segment.

Use of Estimates

The consolidated financial statements of the Company have been prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”). In preparing the consolidated financial statements, management is required to make estimates and assumptions, which significantly affect the reported amounts in the consolidated financial statements. Such estimates include the valuation of loans, goodwill, intangible assets, indemnification assets, and other long-lived assets, along with assumptions used in the calculation of income taxes, among others. These estimates and assumptions are based on management's best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using experience and other factors, including the current economic environment, which management believes to be reasonable under the circumstances. Management adjusts such estimates and assumptions when facts and circumstances dictate. Decreased real estate values, volatile credit markets, and unemployment have combined to increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in those estimates resulting from continuing changes in the economic environment will be reflected in the financial statements in future periods.

Cash Flow Information

For purposes of reporting cash flows, the Company considers cash and due from banks, interest-bearing deposits and federal funds sold that mature within 90 days of the balance sheet date to be cash and cash equivalents. At December 31, 2017 and 2016, approximately $17.5 million, and $18.2 million, respectively, of cash and due from banks represented required reserves on deposits maintained by the Company in accordance with Federal Reserve Bank requirements.

Investments

The Company has classified all investments in debt securities as available for sale or held to maturity.

Securities classified as available for sale are carried at fair value. Unrealized holding gains and losses for available for sale securities are excluded from earnings and reported as a net amount in a separate component of shareholders' equity until realized. All previous fair value adjustments included in the separate component of shareholders' equity are reversed upon sale.

Securities classified as held to maturity are carried at historical cost and adjusted for amortization of premiums and accretion of discounts.

Declines in the fair value of securities below their cost deemed to be other-than-temporary are reflected in operations as realized losses. In estimating other-than-temporary impairment losses, management systematically evaluates investment securities for other-than-temporary declines in fair value on a quarterly basis. This analysis requires management to consider various factors, which include (1) the present value of the cash flows expected to be collected compared to the amortized cost of the security, (2) duration and magnitude of the decline in value, (3) the financial condition of the issuer or issuers, (4) structure of the security, and (5) the intent to sell the security or whether it's more likely than not the Company would be required to sell the security before its anticipated recovery in market value.

Premiums and discounts are amortized or accreted over the expected lives of the respective securities as an adjustment to yield using the interest method. Dividend and interest income is recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold.

Loans Held for Sale

The Company provides long-term financing of one-to-four-family residential real estate by originating fixed and variable rate loans. Long-term fixed and variable rate loans are sold into the secondary market with limited recourse. Upon receipt of an application for a real estate loan, the Company determines whether the loan will be sold into the secondary market or retained in the Company's loan portfolio. The interest rates on the loans sold are locked with the buyer and the Company bears no interest rate risk related to these loans. Mortgage loans held for sale are carried at the lower of cost or fair value, which is determined on a specific identification method. The Company does not retain servicing on any loans sold, nor did the Company have any capitalized mortgage servicing rights at December 31, 2017 or 2016. Gains on the sale of loans held for sale are reported net of direct origination fees and costs in the Company's consolidated statements of operations.

Portfolio Loans

Loans are reported at the principal balance outstanding, net of unearned fees, costs, and premiums or discounts on acquired loans. Loan origination fees, direct origination costs, and premiums or discounts resulting from acquired loans are deferred and recognized over the lives of the related loans as a yield adjustment using the interest method.

Interest income on loans is accrued to income based on the principal amount outstanding. The recognition of interest income is discontinued when a loan becomes 90 days past due or a significant deterioration in the borrower's credit has occurred which, in management's judgment, negatively impacts the collectibility of the loan. Unpaid interest on such loans is reversed at the time the loan becomes uncollectible and subsequent interest payments received are applied to principal if any doubt exists as to the collectibility of such principal; otherwise, such receipts are recorded as interest income. Loans that have not been restructured are returned to accrual status when management believes full collectibility of principal and interest is expected. Non-accrual loans that have been restructured will remain in a non-accrual status until the borrower has made at least six months of consecutive contractual payments.

Purchased Credit Impaired ("PCI") Loans

PCI loans were acquired in a business combination or transaction, that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments receivable. PCI loans were initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance. The difference between the undiscounted cash flows expected at acquisition and the investment in the loans, or the “accretable yield,” is recognized as interest income on a level-yield method over the life of the loans. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “nonaccretable difference,” are not recognized as a yield adjustment or as a loss accrual or a valuation allowance. The Company aggregates individual loans with common risk characteristics into pools of loans. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loans over their remaining lives. Decreases in expected cash flows due to an inability to collect contractual cash flows are recognized as impairment through the provision for loan losses account. Any allowance for loan loss on these pools reflect only losses incurred after the acquisition. Disposals of loans, including sales of loans, paydowns, payments in full or foreclosures result in the removal or reduction of the loan from the loan pool.

PCI loans are generally considered accruing and performing, as the loans accrete income over the estimated life of the loan, in circumstances where cash flows are reasonably estimable by management. Accordingly, PCI loans that could be contractually past due could be considered to be accruing and performing. If the timing and amount of future cash flows is not reasonably estimable or is less than the carrying value, the loans may be classified as nonaccrual loans and the purchase price discount on those loans is not recorded as interest income until the timing and amount of future cash flows can be reasonably estimable.

Impaired Loans

Loans are considered “impaired” when it becomes probable that the Company will be unable to collect all amounts due according to the loan's contractual terms. Non-accrual loans, loans past due greater than 90 days and still accruing, unless adequately secured and in the process of collection, and restructured loans qualify as “impaired loans.” Restructured loans involve the granting of a concession to a borrower experiencing financial difficulty involving the modification of terms of the loan, such as changes in payment schedule or interest rate.

When measuring impairment, the expected future cash flows of an impaired loan are discounted at the loan's effective interest rate at origination. Alternatively, impairment can be measured by reference to an observable market price, if one exists, or the fair value of the collateral for a collateral-dependent loan. Interest income on impaired loans is not accrued but is recorded when cash is received and only if principal is considered to be fully collectible. Loans and leases, which are deemed uncollectible, are charged off to the allowance for loan losses, while recoveries of amounts previously charged off are credited to the allowance for loan losses.

Impaired loans exclude PCI loans, as described above. Although, if the timing and amount of future cash flows is not reasonably estimable, the loans may be classified as nonaccrual loans and the purchase price discount on those loans is not recorded as interest income until the timing and amount of future cash flows can be reasonably estimated. See Note 5 – Loans for more information on these loans.

Loans are generally placed on non-accrual status when contractually past due 90 days or more as to interest or principal payments. Additionally, whenever management becomes aware of facts or circumstances that may adversely impact the collectability of principal or interest on loans, it is management's practice to place such loans on non-accrual status immediately, rather than delaying such action until the loans become 90 days past due. Previously accrued and uncollected interest on such loans is reversed. Income is recorded only to the extent that a determination has been made that the principal balance of the loan is collectable and the interest payments are subsequently received in cash, or for a restructured loan, the borrower has made six consecutive contractual payments. If collectability of the principal is in doubt, payments received are applied to loan principal.

Loans past due 90 days or more but still accruing interest are also generally included in nonperforming loans. Loans past due 90 days or more but still accruing are classified as such where the underlying loans are both well secured (the collateral value is sufficient to cover principal and accrued interest) and are in the process of collection. At December 31, 2017, we did not have any loans past due greater than 90 days and not included in nonperforming loans.

Loan Charge-Offs

Loans are charged-off when the primary and secondary sources of repayment (cash flow, collateral, guarantors, etc.) are less than their carrying value.

Allowance For Loan Losses

The allowance for loan losses is increased by provision charged to expense and is available to absorb charge-offs, net of recoveries. Management utilizes a systematic, documented approach in determining the appropriate level of the allowance for loan losses. The level of the allowance reflects management's continuing evaluation of industry concentrations; specific credit risks; loan loss experience; current loan portfolio quality; present economic, political and regulatory conditions; and probable losses inherent in the current loan portfolio. The determination of the appropriate level of the allowance for loan losses inherently involves a degree of subjectivity and requires that the Company make significant estimates of current credit risks and future trends, all of which may undergo material changes. Changes in economic conditions affecting borrowers, new information regarding existing loans, identification of additional problem loans and other factors, both within and outside of our control, may require an increase in the allowance for loan losses.

Management believes the allowance for loan losses is adequate to absorb inherent losses in the loan portfolio. While management uses available information to recognize losses on loans, future additions to the allowance may be necessary based on changes in economic conditions and other factors. In addition, various regulatory agencies, as an integral part of the examination process, periodically review the Bank's loan portfolio. Such agencies may require additions to the allowance for loan losses based on their judgments and interpretations of information available to them at the time of their examinations.

Allowance for Loan Losses on PCI Loans

The Company updates its cash flow projections for PCI loans on a periodic basis. Assumptions utilized in this process include projections related to probability of default, loss severity, prepayment, extensions and recovery lag. Projections related to probability of default and prepayment are calculated utilizing a loan migration analysis and management's assessment of loss exposure including the fair value of underlying collateral. The loan migration analysis is a matrix that specifies the probability of a loan pool transitioning into a particular delinquency or liquidation state given its current performance at the measurement date. Loss severity factors are based upon industry data and historical experience.

Any decreases in expected cash flows after the acquisition date and subsequent measurement periods are recognized by recording an impairment in allowance for loan losses.

Other Real Estate

Other real estate represents property acquired through foreclosure or deeded to the Company in lieu of foreclosure on loans on which the borrowers have defaulted on the payment of principal or interest. Other real estate is recorded on an individual asset basis at the lower of cost or fair value less estimated costs to sell. The fair value of other real estate is based upon estimates of future cash flows, market value of similar assets, if available, or independent appraisals. These estimates involve significant uncertainties and judgments. As a result, fair value estimates may not be realizable in a current sale or settlement of the other real estate. Subsequent reductions in fair value are expensed within noninterest expense.

Gains and losses resulting from the sale of other real estate are credited or charged to current period earnings. Costs of maintaining and operating other real estate are expensed as incurred, and expenditures to complete or improve other real estate properties are capitalized if the expenditures are expected to be recovered upon ultimate sale of the property.

Fixed Assets

Buildings, leasehold improvements, furniture, fixtures, equipment, and capitalized software are stated at cost less accumulated depreciation. All categories are computed using the straight-line method over their respective estimated useful lives. Furniture, fixtures and equipment is depreciated over three to ten years, buildings and leasehold improvements over ten to forty years, and capitalized software over three years based upon estimated lives or lease obligation periods.

State Tax Credits Held for Sale

The Company has purchased the rights to receive 10-year streams of state tax credits at agreed upon discount rates and sells such tax credits to its clients and others. All state tax credits purchased prior to 2009 are accounted for at fair value. All state tax credits purchased since 2009 are accounted for at cost. The Company elected not to account for the state tax credits purchased since 2009 at fair value in order to limit the volatility of the fair value changes in the Company's consolidated statements of operations.

Cash Surrender Value of Life Insurance

The Company has purchased bank-owned life insurance policies on certain bank officers. Bank-owned life insurance is recorded at its cash surrender value. Changes in the cash surrender values are included in noninterest income.

Federal Home Loan Bank Stock

The Bank, as a member of the Federal Home Loan Bank of Des Moines (“FHLB”), is required to maintain an investment in the capital stock of the FHLB. The stock is redeemable at par by the FHLB, and is, therefore, carried at cost and periodically evaluated for impairment. The Company records FHLB dividends in interest income.

Goodwill and Other Intangible Assets

The Company tests goodwill for impairment on an annual basis and whenever events or changes in circumstances indicate that the Company may not be able to recover the respective asset's carrying amount. The Company's annual test for impairment was performed in the fourth quarter of December 31, 2017. Such tests involve the use of estimates and assumptions. Core deposit intangibles are amortized using an accelerated method over an estimated useful life of approximately 10 years.

Potential impairments to goodwill must first be identified by performing a qualitative assessment which evaluates relevant events or circumstances to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If this test indicates it is more likely than not that goodwill has been impaired, then a quantitative impairment test is completed. The quantitative impairment test calculates the fair value of the reporting unit and compares it with its carrying amount, including goodwill. If the carrying amount of goodwill exceeds its implied fair market value, an impairment loss is recognized. That loss is equal to the carrying amount of goodwill that is in excess of its implied fair market value.

Impairment of Long-Lived Assets

Long-lived assets, such as fixed assets and purchased intangibles subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets to be disposed of are separately presented in the balance sheet and reported at the lower of the carrying amount or fair value less costs to sell, and are no longer depreciated. The assets and liabilities of a disposal group classified as held for sale are presented separately in the appropriate asset and liability sections of the balance sheet.

Derivative Financial Instruments and Hedging Activities

The Company uses derivative financial instruments to assist in the management of interest rate sensitivity and to modify the repricing, maturity and option characteristics of certain assets and liabilities. In addition, the Company also offers an interest rate hedge program that includes interest rate swaps to assist its customers in managing their interest rate risk profile. In order to eliminate the interest rate risk associated with offering these products, the Company enters into derivative contracts with third parties to offset the customer contracts.

Derivative instruments are required to be measured at fair value and recognized as either assets or liabilities in the consolidated financial statements. Fair value represents the payment the Company would receive or pay if the item were sold or bought in a current transaction. The accounting for changes in fair value (gains or losses) of a hedged item is dependent on whether the related derivative is designated and qualifies for “hedge accounting.” The Company assigns derivatives to one of these categories at the purchase date: cash flow hedge, fair value hedge, or non-designated derivatives. An assessment of the expected and ongoing hedge effectiveness of any derivative designated a fair value hedge or cash flow hedge is performed as required by the accounting standards. Derivatives are included in other assets and other liabilities in the consolidated balance sheets. Generally, the only derivative instruments used by the Company have been interest rate swaps and interest rate caps.

The Company does not currently have derivative instruments designated as fair value or cash flow hedges. Certain derivative financial instruments are not designated as cash flow or as fair value hedges for accounting purposes. These non-designated derivatives are intended to provide interest rate protection on net interest income or noninterest income but do not meet hedge accounting treatment. Customer accommodation interest rate swap contracts are not designated as hedging instruments. Changes in the fair value of these instruments are recorded in interest income or noninterest income in the consolidated statements of income depending on the underlying hedged item.

Income Taxes

The Company and its subsidiaries file a consolidated federal income tax return. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. We evaluated the need for deferred tax asset valuation allowances based on a more-likely-than-not standard. The ability to realize deferred tax assets depends on the ability to generate sufficient positive taxable income within the carryback or carryforward periods provided for in the laws for each applicable taxing jurisdiction. We consider the following possible sources of taxable income: future reversal patterns of existing taxable temporary differences, future taxable income exclusive of reversing temporary differences, taxable income in prior carryback years and the availability of qualified tax planning strategies. The assessment regarding whether a valuation allowance is required or should be adjusted depends on all available positive and negative factors including, but not limited to, nature, frequency, and severity of recent losses, duration of available carryforward periods, experience with tax attributes expiring unused and near and medium term financial outlook. Because of the complexity of tax laws and regulations, interpretation can be difficult and subject to legal judgment given specific facts and circumstances. It is possible that others, given the same information, may at any point in time reach different reasonable conclusions regarding the estimated amounts of accrued taxes.

The SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Cuts and Jobs Act of 2017 (“Tax Act”). SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. The Company has recorded amounts based on the information known and reasonable estimates used as of December 31, 2017, but are subject to change based on a number of factors. The Company will complete its analysis of certain tax positions at the time it files its tax returns for the year ended December 31, 2017 and will be able to conclude if any further adjustments to the provisional estimate of the impact recorded is required.

Stock-Based Compensation

Stock-based compensation is recognized as an expense for stock options, restricted stock awards, and restricted stock units granted to employees in return for employee service. Equity classified awards are measured at the grant date fair value using either an observable market value or a valuation methodology, and recognized over the requisite service period on a straight-line basis. Forfeitures are recorded as they occur. A description of the Company's stock-based employee compensation plan is described in Note 15 - Compensation Plans.

Acquisitions and Divestitures

Acquisitions and business combinations are accounted for using the acquisition method of accounting. The assets and liabilities of the acquired entities have been recorded at their estimated fair values at the date of acquisition. Goodwill represents the excess of the purchase price over the fair value of net assets acquired, including the amount assigned to identifiable intangible assets.

The purchase price allocation process requires an estimation of the fair values of the assets acquired and the liabilities assumed. When a business combination agreement provides for an adjustment to the cost of the combination contingent on future events, the Company includes an estimate of the acquisition-date fair value as part of the cost of the combination. To determine the fair values, the Company relies on third party valuations, such as appraisals, or internal valuations based on discounted cash flow analyses or other valuation techniques. The results of operations of the acquired business are included in the Company's consolidated financial statements from the date of acquisition. Merger-related costs are costs the Company incurs to effect a business combination. In 2017, the Company changed its presentation of Merger related expenses as a separate component of Noninterest expenses on the Condensed Consolidated Statements of Operations. Merger related expenses include costs directly related to merger or acquisition activity and include legal and professional fees, system consolidation and conversion costs, and compensation costs such as severance and retention incentives for employees impacted by acquisition activity. The Company accounts for merger-related costs as expenses in the periods in which the costs are incurred and the services are received.

For divestitures, the Company measures an asset (disposal group) classified as held for sale at the lower of its carrying value at the date the asset is initially classified as held for sale or its fair value less costs to sell. The Company reports the results of operations of an entity or group of components that either has been disposed of or held for sale as discontinued operations only if the disposal of that component represents a strategic shift that has or will have a major effect on an entity's operations and financial results.

Any incremental direct costs incurred to transact the sale are allocated against the gain or loss on the sale. These costs would include items like legal fees, title transfer fees, broker fees, etc. Any goodwill and intangible assets associated with the portion of the reporting unit to be disposed of is included in the carrying amount of the business in determining the gain or loss on the sale.

Basic and Diluted Earnings Per Common Share

Basic earnings per common share data is calculated by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. Common shares outstanding include common stock and restricted stock awards where recipients have satisfied the vesting terms. Diluted earnings per common share gives effect to all dilutive potential common shares outstanding during the period using the treasury stock method.

Consolidated Statement of Comprehensive Income

The Consolidated Statement of Comprehensive Income includes the amount and the related tax impact that have been reclassified from accumulated other comprehensive income to net income. The classification adjustment for unrealized loss/gain on sale of securities included in net income has been recorded through the gain on sale of investment securities line item, within noninterest income, in the Company's Consolidated Statements of Operations.

Reclassifications

Some items in the prior year financial statements were reclassified to conform to the current presentation. In 2017, the Company changed its presentation of loans on the face of the Consolidated Balance Sheets to combine originated loans with purchased loans. See Note 5 - Loans for more information. The Company also changed its presentation of the Noninterest Income section on the face of the Consolidated Statements of Operations to separate card services revenue from other service charges and fee income. The difference was reclassified into miscellaneous income. Merger related expenses were reclassified from other expenses to be a separate component of the Noninterest Expense section on the Consolidated Statements of Operations. Reclassifications had no effect on prior year net income or shareholders' equity.