Nature of Operations and Summary of Significant Accounting Policies Nature of Operations and Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting	Nature of Operations. The accounting and reporting practices of First Business Financial Services, Inc. (the “Corporation”), through our wholly-owned subsidiary, First Business Bank (“FBB”, or the “Bank”), has been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). FBB operates as a commercial banking institution primarily in the Wisconsin and greater Kansas City markets. FBB also offers trust and investment services through First Business Trust & Investments (“FBTI”), a division of FBB. The Bank provides a full range of financial services to businesses, business owners, executives, professionals and high net worth individuals. The Bank is subject to competition from other financial institutions and service providers and is also subject to state and federal regulations. FBB has the following wholly-owned subsidiaries: First Business Capital Corp. (“FBCC”), First Madison Investment Corp. (“FMIC”), First Business Equipment Finance, LLC (“FBEF”), ABKC Real Estate, LLC (“ABKC”), Rimrock Road Investment Fund, LLC (“Rimrock Road”), BOC Investment, LLC (“BOC”), Mitchell Street Apartments Investment, LLC (“Mitchell Street”), and FBB Tax Credit Investment LLC (“FBB Tax Credit”). FMIC is located in and was formed under the laws of the state of Nevada.
Principles of Consolidation	Basis of Financial Statement Presentation. The Consolidated Financial Statements include the accounts of the Corporation and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. In accordance with the provisions of Accounting Standards Codification (“ASC”) Topic 810, the Corporation’s ownership interest in FBFS Statutory Trust II (“Trust II”) has not been consolidated into the financial statements.
Use of Estimates	Management of the Corporation is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements as well as reported amounts of revenues and expenses during the reporting period. Actual results could differ significantly from those estimates. Material estimates that could significantly change in the near-term include the value of securities, level of the allowance for loan and lease losses, lease residuals, property under operating leases, goodwill, level of the Small Business Administration (“SBA”) recourse reserve and income taxes.
Reclassification	Certain amounts in prior periods may have been reclassified to conform to the current presentation.
Subsequent Events	Subsequent events have been evaluated through the date of the issuance of the Consolidated Financial Statements. No significant subsequent events have occurred through this date requiring adjustment to the financial statements or disclosures.
Cash and Cash Equivalents	Cash and Cash Equivalents. The Corporation considers federal funds sold, interest-bearing deposits and short-term investments that have original maturities of three months or less to be cash equivalents.
Securities	Securities. The Corporation classifies its investment and mortgage-related securities as available-for-sale, held-to-maturity and trading. Debt securities that the Corporation has the positive intent and ability to hold to maturity are classified as held-to-maturity and are stated at amortized cost. Debt and equity securities bought expressly for the purpose of selling in the near term are classified as trading securities and are measured at fair value with unrealized gains and losses reported in earnings. Debt and equity securities not classified as held-to-maturity or as trading are classified as available-for-sale. Available-for-sale securities are measured at fair value with unrealized gains and losses reported as a separate component of stockholders’ equity, net of tax. Realized gains and losses, and declines in value deemed to be other than temporary, are included in the consolidated statements of income as a component of non-interest income. The cost of securities sold is based on the specific identification method. The Corporation did not hold any trading securities at December 31, 2017 or 2016. Discounts and premiums on securities are accreted and amortized into interest income using the effective yield method over the weighted average life of the securities. Declines in the fair value of investment securities (with certain exceptions for debt securities noted below) that are deemed to be other-than-temporary are charged to earnings as a realized loss and a new cost basis for the securities is established. In evaluating other-than-temporary impairment, management considers the length of time and extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer and the intent and ability of the Corporation to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in fair value in the near term. Declines in the fair value of debt securities below amortized cost are deemed to be other-than-temporary in circumstances where: (1) the Corporation has the intent to sell a security; (2) it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis; or (3) the Corporation does not expect to recover the entire amortized cost basis of the security. If the Corporation intends to sell a security or if it is more likely than not that the Corporation will be required to sell the security before recovery, an other-than-temporary impairment write-down is recognized in earnings equal to the difference between the security’s amortized cost basis and its fair value. If the Corporation does not intend to sell the security or it is not more likely than not that it will be required to sell the security before recovery, the other-than-temporary impairment write-down is separated into an amount representing credit loss, which is recognized in earnings, and an amount related to all other factors, which is recognized in other comprehensive income.
Loans Held for Sale	Loans Held for Sale. Residential real estate loans and the guaranteed portions of SBA loans which are originated and intended for sale in the secondary market are classified as held for sale. These loans are carried at the lower of cost or fair value in the aggregate. Unrealized losses on such loans are recognized through a valuation allowance by a charge to other non-interest income. Gains and losses on the sale of loans are also included in other non-interest income. As assets specifically originated for sale, the origination of, disposition of, and gain/loss on these loans are classified as operating activities in the statement of cash flows. Fees received from the borrower and direct costs to originate the loans are deferred and recognized as part of the gain or loss on sale. There was $2.2 million and $1.1 million in loans held for sale outstanding at December 31, 2017 and 2016, respectively.
Loans and Leases	Loans and Leases. Loans and leases which management has the intent and ability to hold for the foreseeable future or until maturity are reported at their outstanding principal balance with adjustments for partial charge-offs, the allowance for loan and lease losses, deferred fees or costs on originated loans and leases and unamortized premiums or discounts on any purchased loans. A loan or a lease is accounted for as a troubled debt restructuring if the Corporation, for economic or legal reasons related to the borrower’s financial condition, grants a concession to the borrower that it 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 lease or a modification of terms, such as a reduction of the stated interest rate or face amount of the loan or lease, a reduction of accrued interest, an extension of the maturity date at a stated interest rate lower than the current market rate for a new loan or lease with similar risk or some combination of these concessions. Restructured loans can involve loans remaining on non-accrual, moving to non-accrual or continuing on accrual status, depending on individual facts and circumstances. Non-accrual restructured loans are included and treated with all other non-accrual loans. In addition, all accruing restructured loans are reported as troubled debt restructurings which are considered and accounted for as impaired loans. Generally, restructured loans remain on non-accrual until the borrower has attained a sustained period of repayment performance under the modified loan terms (generally a minimum of six months). However, performance prior to the restructuring, or significant events that coincide with the restructuring, are considered in assessing whether the borrower can meet the new terms and whether the loan should be returned to or maintained on accrual status. If the borrower’s ability to meet the revised payment schedule is not reasonably assured, the loan remains on non-accrual. Interest on non-impaired loans and leases is accrued and credited to income on a daily basis based on the unpaid principal balance and is calculated using the effective interest method. Per policy, a loan or a lease is considered impaired and placed on non-accrual status when it becomes 90 days past due or it is doubtful that contractual principal and interest will be collected in accordance with the terms of the contract. A loan or lease is determined to be past due if the borrower fails to meet a contractual payment and will continue to be considered past due until all contractual payments are received. When a loan or lease is placed on non-accrual, the interest accrual is discontinued and previously accrued but uncollected interest is deducted from interest income. If collectability of the contractual principal and interest is in doubt, payments received are first applied to reduce the loan principal. If collectability of the contractual payments is not in doubt, payments may be applied to interest for interest amounts due on a cash basis. As soon as it is determined with certainty that the principal of an impaired loan or lease is uncollectable, either through collections from the borrower or disposition of the underlying collateral, the portion of the carrying balance that exceeds the estimated measurement value of the loan or lease is charged off. Loans or leases are returned to accrual status when they are brought current in terms of both principal and accrued interest due, have performed in accordance with contractual terms for a reasonable period of time and when the ultimate collectability of total contractual principal and interest is no longer doubtful. Transfers of assets, including but not limited to the guaranteed portions of SBA loans and participation interests in other originated loans, that upon completion of the transfer satisfy the conditions to be reported as a sale, including legal isolation, are derecognized from the Consolidated Financial Statements. Transfers of assets that upon completion of the transfer do not meet the conditions of a sale are recorded on a gross basis with a secured borrowing identified to reflect the amount of the transferred interest. Loan and lease origination fees as well as certain direct origination costs are deferred and amortized as an adjustment to loan yields over the stated term of the loan or lease. Loans or leases that result from a refinance or restructuring, other than a troubled debt restructuring, where terms are at least as favorable to the Corporation as the terms for comparable loans to other borrowers with similar collection risks and result in an essentially new loan or lease, are accounted for as a new loan or lease. Any unamortized net fees, costs or penalties are recognized when the new loan or lease is originated. Unamortized net loan or lease fees or costs for loans and leases that result from a refinance or restructure with only minor modifications to the original loan or lease contract are carried forward as a part of the net investment in the new loan or lease. For troubled debt restructurings, all fees received in connection with a modification of terms are applied as a reduction of the loan or lease and any related costs, including direct loan origination costs, are charged to expense as incurred. The Corporation purchased an individual loan in 2013 and a group of loans in connection with the Alterra acquisition which have shown evidence of credit deterioration since origination. These purchased loans are recorded at fair value, such that there is no carryover of the seller’s allowance for loan losses. Such purchased loans are accounted for individually. At acquisition, the Corporation estimates the amount and timing of expected cash flows for each purchased loan and the expected cash flows in excess of fair value are recorded as interest income over the remaining life of the loan (accretable yield). The excess of the loan’s contractual principal and interest over expected cash flows at acquisition is not recorded (nonaccretable difference). Over the life of the loan, expected cash flows continue to be estimated. If the present value of expected cash flows is less than the carrying amount, losses are recognized by an increase in the allowance for loan losses. If the present value of expected cash flows is greater than the carrying amount, it is recognized as part of future interest income.
Allowance for Loan and Lease Losses	To determine the level and composition of the allowance for loan and lease losses, the Corporation categorizes the portfolio into segments with similar risk characteristics. First, the Corporation evaluates loans and leases for potential impairment classification. The Corporation analyzes each loan and lease determined to be impaired on an individual basis to determine a specific reserve based upon the estimated value of the underlying collateral for collateral-dependent loans, or alternatively, the present value of expected cash flows. The Corporation applies historical trends from established risk factors to each category of loans and leases that has not been individually evaluated for the purpose of establishing the general portion of the allowance.
Net Investment in Direct Financing Leases and Operating Leases	Net Investment in Direct Financing Leases. The net investment in direct financing lease agreements represents total undiscounted payments plus estimated unguaranteed residual value (approximating 3% to 20% of the cost of the related equipment) and is recorded as lease receivables when the lease is signed and the leased property is delivered to the client. The excess of the minimum lease payments and residual values over the cost of the equipment is recorded as unearned lease income. Unearned lease income is recognized over the term of the lease on a basis which results in an approximate level rate of return on the unrecovered lease investment. Lease payments are recorded when due under the lease contract. Residual values are established at lease inception equal to the estimated value to be received from the equipment following termination of the initial lease and such estimated value considers all relevant information and circumstances regarding the equipment. In estimating the equipment’s fair value at lease termination, the Corporation relies on internally or externally prepared appraisals, published sources of used equipment prices and historical experience adjusted for known current industry and economic trends. The Corporation’s estimates are periodically reviewed to ensure reasonableness; however, the amounts the Corporation will ultimately realize could differ from the estimated amounts. When there are other than temporary declines in the Corporation’s carrying amount of the unguaranteed residual value, the carrying value is reduced and charged to non-interest expense. Operating Leases. Machinery and equipment are leased to clients under operating leases and are recorded at cost. Equipment under such leases is depreciated over the estimated useful life or term of the lease, if shorter. The impairment loss, if any, would be charged to expense in the period it becomes evident. Rental income is recorded on the straight-line accrual basis as other non-interest income.
Leasehold Improvements and Equipment	Premises and Equipment, net. The cost of buildings and capitalized leasehold improvements is amortized on the straight-line method over the lesser of the term of the respective lease or estimated economic life. Equipment is stated at cost less accumulated depreciation and amortization which is calculated by the straight-line method over the estimated useful lives of three to ten years. Maintenance and repair costs are charged to expense as incurred. Improvements which extend the useful life are capitalized and depreciated over the remaining useful life of the assets.
Foreclosed Properties	Foreclosed Properties. Property acquired by repossession, foreclosure or by deed in lieu of foreclosure is carried at the lower of the recorded investment in the loan at the time of acquisition or the fair value of the underlying property, less costs to sell. Any write-down in the carrying value of a loan or lease at the time of acquisition is charged to the allowance for loan and lease losses. Any subsequent write-downs to reflect current fair value, as well as gains and losses on disposition and revenues are recorded in non-interest expense. Costs relating to the development and improvement of the property are capitalized while holding period costs are charged to other non-interest expense.
Bank-Owned Life Insurance	Bank-Owned Life Insurance. Bank-owned life insurance (“BOLI”) is reported at the amount that would be realized if the life insurance policies were surrendered on the balance sheet date. BOLI policies owned by the Bank are purchased with the objective to fund certain future employee benefit costs with the death benefit proceeds. The cash surrender value of such policies is recorded in bank-owned life insurance on the Consolidated Balance Sheets and changes in the value are recorded in non-interest income. The total death benefit of all BOLI policies was $97.7 million and $97.3 million as of December 31, 2017 and 2016, respectively. There are no restrictions on the use of BOLI proceeds nor are there any contractual restrictions on the ability to surrender the policy. As of each of December 31, 2017 and 2016, there were no borrowings against the cash surrender value of the BOLI policies.
Regulatory Required Holdings	Federal Home Loan Bank and Federal Reserve Bank Stock. The Bank is required to maintain Federal Home Loan Bank (“FHLB”) stock as members of the FHLB, and in amounts as required by these institutions. Alterra, previously as a state chartered member of the Federal Reserve Bank of Kansas City, was required to own shares of Federal Reserve Bank (“FRB”) stock. These equity securities are “restricted” in that they can only be sold back to the respective institutions or another member institution at par. Therefore, they are less liquid than other marketable equity securities and their fair value is equal to cost. At December 31, 2017 and 2016, the Bank had FHLB stock of $1.1 million and $1.8 million, respectively. Alterra had FRB stock of $1.1 million at December 31, 2016. The Corporation periodically evaluates its holding in FHLB and FRB stock for impairment. Should the stock be impaired, it would be written down to its estimated fair value. There were no impairments recorded on FHLB and FRB stock during the year ended December 31, 2017 or 2016.
Goodwill and Intangible Assets	Goodwill and Other Intangible Assets. Goodwill and other intangible assets consist primarily of goodwill, core deposit intangibles and loan servicing rights. Core deposit intangibles have estimated finite lives and are amortized on an accelerated basis to expense over a period of seven years. Loan servicing rights, when purchased, are initially recorded at fair value and subsequently amortized in proportion to and over the period of estimated net servicing income. The Corporation reviews other intangible assets for impairment at least annually, or whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, in which case an impairment charge would be recorded. Goodwill is not amortized but is subject to impairment tests on at least an annual basis, and more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount (including goodwill). An initial qualitative evaluation is made to assess the likelihood of impairment and determine whether further quantitative testing to calculate the fair value is necessary. When the qualitative evaluation indicates that impairment is more likely than not, quantitative testing is required whereby the fair value of each reporting unit is calculated and compared to the recorded book value, “step one.” If the calculated fair value of the reporting unit exceeds its carrying value, goodwill is not considered impaired and “step two” is not considered necessary. If the carrying value of a reporting unit exceeds its calculated fair value, the impairment test continues (“step two”) by comparing the carrying value of the reporting unit’s goodwill to the implied fair value of goodwill. The implied fair value is computed by adjusting all assets and liabilities of the reporting unit to current fair value with the offset adjustment to goodwill. The adjusted goodwill balance is the implied fair value of the goodwill. An impairment charge is recognized if the carrying value of goodwill exceeds the implied fair value of goodwill. See Note 6 for additional information on goodwill and other intangible assets.
SBA Recourse Reserve [Policy Text Block]	SBA Recourse Reserve. The Corporation establishes SBA recourse reserves on the guaranteed portions of sold SBA loans when it is probable that the guarantee may be ineligible. The recourse reserve is reported in accrued interest payable and other liabilities on the Consolidated Balance Sheets and consists of two components: (1) specific reserves for individually evaluated impaired loans that present a collateral shortfall where the guaranty associated with the sold portion of the SBA loan is determined to most likely be ineligible; and (2) general reserves for estimated probable losses on the remaining sold portfolio. The general reserve methodology is based on the evaluation of several factors, including but not limited to: credit quality trends within the SBA portfolio, changes in underlying collateral and the Corporation’s ability to originate, fund or service sold SBA loans in accordance with SBA regulations. In the ordinary course of business, the Corporation sells the guaranteed portions of SBA loans to third parties. The Corporation has a continuing involvement in each of the transferred lending arrangements by way of relationship management, servicing the loans, as well as being subject to normal and customary requirements of the SBA loan program; however, there are no further obligations to the third-party participant required of the Corporation, other than standard representations and warranties related to sold amounts. In the event of a loss resulting from default and a determination by the SBA that there is a deficiency in the manner in which the loan was originated, funded or serviced by the Corporation, the SBA may require the Corporation to repurchase the loan, deny its liability under the guaranty, reduce the amount of the guaranty, or, if it has already paid under the guaranty, seek recovery of the principal loss related to the deficiency from the Corporation. The Corporation must comply with applicable SBA regulations in order to maintain the guaranty. In addition, the Corporation retains the option to repurchase the sold guaranteed portion of an SBA loan if the loan defaults. See Note 18 for additional information on the SBA recourse reserve.
Other Investments	Other Investments. The Corporation owns certain equity investments in other corporate organizations which are not consolidated because the Corporation does not own more than a 50% interest or exercise control over the organization. Investments in corporations representing at least a 20% interest are generally accounted for using the equity method and investments in corporations representing less than 20% interest are generally accounted for at cost. Investments in limited partnerships representing from at least a 3% up to a 50% interest in the entity are generally accounted for using the equity method and investments in limited partnerships representing less than 3% are generally accounted for at cost. All of these investments are periodically evaluated for impairment. Should an investment be impaired, it would be written down to its estimated fair value. The equity investments are reported in other assets and the income and expense from such investments, if any, is reported in non-interest income and non-interest expense.
Derivative Instruments	Derivative Instruments. The Corporation uses derivative instruments to protect against the risk of adverse price or interest rate movements on the value of certain assets, liabilities, future cash flows and economic hedges for written client derivative contracts. Derivative instruments represent contracts between parties that usually require little or no initial net investment and result in one party delivering cash to the other party based on a notional amount and an underlying variable, as specified in the contract, and may be subject to master netting agreements. Market risk is the risk of loss arising from an adverse change in interest rates, exchange rates or equity prices. The Corporation’s primary market risk is interest rate risk. Instruments designed to manage interest rate risk include interest rate swaps, interest rate options and interest rate caps and floors with indices that relate to the pricing of specific assets and liabilities. The nature and volume of the derivative instruments used to manage interest rate risk depend on the level and type of assets and liabilities on the balance sheet and the risk management strategies for the current and anticipated rate environments. Counterparty risk with respect to derivative instruments occurs when a counterparty to a derivative contract with an unrealized gain fails to perform according to the terms of the agreement. Counterparty risk is managed by limiting the counterparties to highly rated dealers, requiring collateral postings when values are in deficit positions, applying uniform credit standards to all activities with credit risk and monitoring the size and the maturity structure of the derivative portfolio. All derivative instruments are to be carried at fair value on the Consolidated Balance Sheets. The accounting for the gain or loss due to changes in the fair value of a derivative instrument depends on whether the derivative instrument qualifies as a hedge. If the derivative instrument does not qualify as a hedge, the gains or losses are reported in earnings when they occur. However, if the derivative instrument qualifies as a hedge, the accounting varies based on the type of risk being hedged. In 2017 and 2016, the Corporation utilized interest rate swaps offered directly to qualified commercial borrowers, which did not qualify for hedge accounting, and therefore, all changes in fair value and gains and losses on these instruments were reported in earnings as they occurred. The effects of netting arrangements are disclosed within the Notes of the Consolidated Financial Statements.
Income Taxes	Income Taxes. Deferred income tax assets and liabilities are computed for temporary differences in timing between the financial statement and tax basis of assets and liabilities that result in taxable or deductible amounts in the future based on enacted tax law and rates applicable to periods in which the differences are expected to affect taxable income. The effect of a change in tax rates on deferred taxes is recognized in income in the period that includes the enactment date. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversals of deferred tax liabilities, appropriate tax planning strategies and projections for future taxable income over the period which the deferred tax assets are deductible. When necessary, valuation allowances are established to reduce deferred tax assets to the realizable amount. Management believes it is more likely than not that the Corporation will realize the benefits of these deductible differences, net of the existing valuation allowances. Income tax expense or benefit represents the tax payable or tax refundable for a period, adjusted by the applicable change in deferred tax assets and liabilities for that period. The Corporation also invests in certain development entities that generate federal and state historic tax credits. The tax benefits associated with these investments are accounted for under the flow-through method and are recognized when the respective project is placed in service. The Corporation and its subsidiaries file a consolidated federal income tax return and separate state income tax returns. Tax sharing agreements allocate taxes to each legal entity for the settlement of intercompany taxes. The Corporation applies a more likely than not standard to each of its tax positions when determining the amount of tax expense or benefit to record in its financial statements. Unrecognized tax benefits are recorded in other liabilities. The Corporation recognizes accrued interest relating to unrecognized tax benefits in income tax expense and penalties in other non-interest expense.
Comprehensive Income	Other Comprehensive Income or Loss. Comprehensive income or loss, shown as a separate financial statement, includes net income or loss, changes in unrealized holding gains and losses on available-for-sale securities, changes in deferred gains and losses on investment securities transferred from available-for-sale to held-to-maturity, if any, changes in unrealized gains and losses associated with cash flow hedging instruments, if any, and the amortization of deferred gains and losses associated with terminated cash flow hedges, if any. For the year ended December 31, 2017, realized securities losses of $403,000 were reclassified out of accumulated other comprehensive income. Realized securities gains of $10,000 were reclassified out of accumulated other comprehensive income for the year ended December 31, 2016.
Earnings Per Share	Earnings Per Common Share. Earnings per common share (“EPS”) is computed using the two-class method. Basic EPS is computed by dividing net income allocated to common shares by the weighted average number of common shares outstanding for the period, excluding any participating securities. Participating securities include unvested restricted shares. Unvested restricted shares are considered participating securities because holders of these securities receive non-forfeitable dividends at the same rate as the holders of the Corporation’s common stock. Diluted EPS is computed by dividing net income allocated to common shares adjusted for reallocation of undistributed earnings of unvested restricted shares by the weighted average number of common shares determined for the basic EPS plus the dilutive effect of common stock equivalents using the treasury stock method based on the average market price for the period.
Segments and Related Information	Segments and Related Information. The Corporation is required to report each operating segment based on materiality thresholds of ten percent or more of certain amounts, such as revenue. Additionally, the Corporation is required to report separate operating segments until the revenue attributable to such segments is at least 75 percent of total consolidated revenue. The Corporation provides a broad range of financial services to individuals and companies in the Midwest. These services include demand, time and savings products, the sale of certain non-deposit financial products and commercial and retail lending, leasing and trust services. While the Corporation’s chief decision-maker monitors the revenue streams of the various products, services and locations, operations are managed and financial performance is evaluated on a corporate-wide basis. The Corporation’s business units have similar basic characteristics in the nature of the products, production processes and type or class of client for products or services; therefore, these business units are considered one operating segment.
Stock Options	Restricted Stock Under the Plan, the Corporation may grant restricted stock to plan participants, subject to forfeiture upon the occurrence of certain events until the dates specified in the participant’s award agreement. While restricted stock is subject to forfeiture, restricted stock participants may exercise full voting rights and will receive all dividends and other distributions paid with respect to the restricted shares. Restricted stock units do not have voting rights and are provided dividend equivalents. The restricted stock granted under the Plan is typically subject to a vesting period. Compensation expense is recognized over the requisite service period of generally four years for the entire award on a straight-line basis. Upon vesting of restricted stock, the benefit of tax deductions in excess of recognized compensation expense is reflected as an income tax benefit in the Consolidated Statements of Income.
Future Accounting Changes	Recent Accounting Pronouncements. In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” with an original effective date for annual reporting periods beginning after December 15, 2016. The ASU is a converged standard between the FASB and the IASB that provides a single comprehensive revenue recognition model for all contracts with customers across transactions and industries. The primary objective of the ASU is revenue recognition that represents the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU No. 2015-14, which defers the effective date of ASU 2014-09 to annual and interim reporting periods in fiscal years beginning after December 15, 2017. Earlier application is permitted only as of annual and interim reporting periods in fiscal years beginning after December 15, 2016. In March 2016, the FASB issued ASU No. 2016-08, “Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net.” The ASU intends to improve the operability and understandability of the implementation guidance of ASU 2014-09 on principal versus agent considerations. In April, May and December 2016, the FASB also issued ASU No. 2016-10, No. 2016-12 and No. 2016-20, respectively, related to Topic 606. The amendments do not change the core principals of the previously issued guidance, but instead further clarify and provide implementation guidance for certain aspects of the original ASU. The Corporation intends to adopt the accounting standards during the first quarter of 2018, as required. The Corporation conducted its assessment of the primary contracts subject to the guidance, including trust and asset management fees, brokerage commissions and deposit service charges. The Corporation has concluded that the adoption of the accounting standard will not have a material impact on the Corporation’s existing revenue recognition practices or on its results of operations, financial position and liquidity. In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842).” The ASU intends to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities and disclosing key information about leasing arrangements. The ASU will require lessees to recognize the following for all leases (with the exception of short-term leases) at the commencement date: (1) a lease liability, which is a lessees’ obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Under the new guidance, lessor accounting is largely unchanged. Certain targeted improvements were made to align, where necessary, lessor accounting with the lessee accounting model and Topic 606, Revenue from Contracts with Customers. The new lease guidance simplifies the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. The ASU is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Corporation intends to adopt the accounting standard during the first quarter of 2019, as required, and is currently evaluating the impact on its results of operations, financial position and liquidity. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments- Credit Losses (Topic 326).” The ASU replaces the incurred loss impairment methodology for recognizing credit losses with a methodology that reflects all expected credit losses. The ASU also requires consideration of a broader range of information to inform credit loss estimates, including such factors as past events, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. The amendments affect loans, debt securities, trade receivables, net investments in leases, off-balance-sheet credit exposures, and any other financial asset not excluded from the scope that have the contractual right to receive cash. Entities will apply the amendments in the ASU through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. The ASU is effective for public companies for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted as of the fiscal years beginning after December 15, 2018. The Corporation intends to adopt the accounting standard during the first quarter of 2020, as required, and is currently evaluating the impact on its results of operations, financial position and liquidity. A cross-functional team has been established to assess and implement the standard. In May 2017, the FASB issued ASU No. 2017-09, “Compensation- Stock Compensation (Topic 718).” The ASU provides clarity about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The ASU is effective for all entities for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. The Corporation is in the process of evaluating the impact of this standard but does not expect this standard to have a material impact on its results of operations, financial position and liquidity. In August 2017, the FASB issued ASU No. 2017-12, “Derivatives and Hedging (Topic 815).” The ASU intends to better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. It also expands and refines hedge accounting for both nonfinancial and financial risk components and aligns the recognition and presentation of the effects of the hedging instrument and the hedged item. The ASU is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The Corporation adopted the standard in the fourth quarter of 2017 with no material impact on its results of operations, financial position and liquidity.

Nature of Operations and Summary of Significant Accounting Policies Nature of Operations and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Accounting

Nature of Operations. The accounting and reporting practices of First Business Financial Services, Inc. (the “Corporation”), through our wholly-owned subsidiary, First Business Bank (“FBB”, or the “Bank”), has been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). FBB operates as a commercial banking institution primarily in the Wisconsin and greater Kansas City markets. FBB also offers trust and investment services through First Business Trust & Investments (“FBTI”), a division of FBB. The Bank provides a full range of financial services to businesses, business owners, executives, professionals and high net worth individuals. The Bank is subject to competition from other financial institutions and service providers and is also subject to state and federal regulations. FBB has the following wholly-owned subsidiaries: First Business Capital Corp. (“FBCC”), First Madison Investment Corp. (“FMIC”), First Business Equipment Finance, LLC (“FBEF”), ABKC Real Estate, LLC (“ABKC”), Rimrock Road Investment Fund, LLC (“Rimrock Road”), BOC Investment, LLC (“BOC”), Mitchell Street Apartments Investment, LLC (“Mitchell Street”), and FBB Tax Credit Investment LLC (“FBB Tax Credit”). FMIC is located in and was formed under the laws of the state of Nevada.

Principles of Consolidation

Basis of Financial Statement Presentation. The Consolidated Financial Statements include the accounts of the Corporation and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. In accordance with the provisions of Accounting Standards Codification (“ASC”) Topic 810, the Corporation’s ownership interest in FBFS Statutory Trust II (“Trust II”) has not been consolidated into the financial statements.

Use of Estimates

Management of the Corporation is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements as well as reported amounts of revenues and expenses during the reporting period. Actual results could differ significantly from those estimates. Material estimates that could significantly change in the near-term include the value of securities, level of the allowance for loan and lease losses, lease residuals, property under operating leases, goodwill, level of the Small Business Administration (“SBA”) recourse reserve and income taxes.

Reclassification

Certain amounts in prior periods may have been reclassified to conform to the current presentation.

Subsequent Events

Subsequent events have been evaluated through the date of the issuance of the Consolidated Financial Statements. No significant subsequent events have occurred through this date requiring adjustment to the financial statements or disclosures.

Cash and Cash Equivalents

Cash and Cash Equivalents. The Corporation considers federal funds sold, interest-bearing deposits and short-term investments that have original maturities of three months or less to be cash equivalents.

Securities

Securities. The Corporation classifies its investment and mortgage-related securities as available-for-sale, held-to-maturity and trading. Debt securities that the Corporation has the positive intent and ability to hold to maturity are classified as held-to-maturity and are stated at amortized cost. Debt and equity securities bought expressly for the purpose of selling in the near term are classified as trading securities and are measured at fair value with unrealized gains and losses reported in earnings. Debt and equity securities not classified as held-to-maturity or as trading are classified as available-for-sale. Available-for-sale securities are measured at fair value with unrealized gains and losses reported as a separate component of stockholders’ equity, net of tax. Realized gains and losses, and declines in value deemed to be other than temporary, are included in the consolidated statements of income as a component of non-interest income. The cost of securities sold is based on the specific identification method. The Corporation did not hold any trading securities at December 31, 2017 or 2016.

Discounts and premiums on securities are accreted and amortized into interest income using the effective yield method over the weighted average life of the securities.

Declines in the fair value of investment securities (with certain exceptions for debt securities noted below) that are deemed to be other-than-temporary are charged to earnings as a realized loss and a new cost basis for the securities is established. In evaluating other-than-temporary impairment, management considers the length of time and extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer and the intent and ability of the Corporation to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in fair value in the near term. Declines in the fair value of debt securities below amortized cost are deemed to be other-than-temporary in circumstances where: (1) the Corporation has the intent to sell a security; (2) it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis; or (3) the Corporation does not expect to recover the entire amortized cost basis of the security. If the Corporation intends to sell a security or if it is more likely than not that the Corporation will be required to sell the security before recovery, an other-than-temporary impairment write-down is recognized in earnings equal to the difference between the security’s amortized cost basis and its fair value. If the Corporation does not intend to sell the security or it is not more likely than not that it will be required to sell the security before recovery, the other-than-temporary impairment write-down is separated into an amount representing credit loss, which is recognized in earnings, and an amount related to all other factors, which is recognized in other comprehensive income.

Loans Held for Sale

Loans Held for Sale. Residential real estate loans and the guaranteed portions of SBA loans which are originated and intended for sale in the secondary market are classified as held for sale. These loans are carried at the lower of cost or fair value in the aggregate. Unrealized losses on such loans are recognized through a valuation allowance by a charge to other non-interest income. Gains and losses on the sale of loans are also included in other non-interest income. As assets specifically originated for sale, the origination of, disposition of, and gain/loss on these loans are classified as operating activities in the statement of cash flows. Fees received from the borrower and direct costs to originate the loans are deferred and recognized as part of the gain or loss on sale. There was $2.2 million and $1.1 million in loans held for sale outstanding at December 31, 2017 and 2016, respectively.

Loans and Leases

Loans and Leases. Loans and leases which management has the intent and ability to hold for the foreseeable future or until maturity are reported at their outstanding principal balance with adjustments for partial charge-offs, the allowance for loan and lease losses, deferred fees or costs on originated loans and leases and unamortized premiums or discounts on any purchased loans.

A loan or a lease is accounted for as a troubled debt restructuring if the Corporation, for economic or legal reasons related to the borrower’s financial condition, grants a concession to the borrower that it 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 lease or a modification of terms, such as a reduction of the stated interest rate or face amount of the loan or lease, a reduction of accrued interest, an extension of the maturity date at a stated interest rate lower than the current market rate for a new loan or lease with similar risk or some combination of these concessions. Restructured loans can involve loans remaining on non-accrual, moving to non-accrual or continuing on accrual status, depending on individual facts and circumstances. Non-accrual restructured loans are included and treated with all other non-accrual loans. In addition, all accruing restructured loans are reported as troubled debt restructurings which are considered and accounted for as impaired loans. Generally, restructured loans remain on non-accrual until the borrower has attained a sustained period of repayment performance under the modified loan terms (generally a minimum of six months). However, performance prior to the restructuring, or significant events that coincide with the restructuring, are considered in assessing whether the borrower can meet the new terms and whether the loan should be returned to or maintained on accrual status. If the borrower’s ability to meet the revised payment schedule is not reasonably assured, the loan remains on non-accrual.

Interest on non-impaired loans and leases is accrued and credited to income on a daily basis based on the unpaid principal balance and is calculated using the effective interest method. Per policy, a loan or a lease is considered impaired and placed on non-accrual status when it becomes 90 days past due or it is doubtful that contractual principal and interest will be collected in accordance with the terms of the contract. A loan or lease is determined to be past due if the borrower fails to meet a contractual payment and will continue to be considered past due until all contractual payments are received. When a loan or lease is placed on non-accrual, the interest accrual is discontinued and previously accrued but uncollected interest is deducted from interest income. If collectability of the contractual principal and interest is in doubt, payments received are first applied to reduce the loan principal. If collectability of the contractual payments is not in doubt, payments may be applied to interest for interest amounts due on a cash basis. As soon as it is determined with certainty that the principal of an impaired loan or lease is uncollectable, either through collections from the borrower or disposition of the underlying collateral, the portion of the carrying balance that exceeds the estimated measurement value of the loan or lease is charged off. Loans or leases are returned to accrual status when they are brought current in terms of both principal and accrued interest due, have performed in accordance with contractual terms for a reasonable period of time and when the ultimate collectability of total contractual principal and interest is no longer doubtful.

Transfers of assets, including but not limited to the guaranteed portions of SBA loans and participation interests in other originated loans, that upon completion of the transfer satisfy the conditions to be reported as a sale, including legal isolation, are derecognized from the Consolidated Financial Statements. Transfers of assets that upon completion of the transfer do not meet the conditions of a sale are recorded on a gross basis with a secured borrowing identified to reflect the amount of the transferred interest.

Loan and lease origination fees as well as certain direct origination costs are deferred and amortized as an adjustment to loan yields over the stated term of the loan or lease. Loans or leases that result from a refinance or restructuring, other than a troubled debt restructuring, where terms are at least as favorable to the Corporation as the terms for comparable loans to other borrowers with similar collection risks and result in an essentially new loan or lease, are accounted for as a new loan or lease. Any unamortized net fees, costs or penalties are recognized when the new loan or lease is originated. Unamortized net loan or lease fees or costs for loans and leases that result from a refinance or restructure with only minor modifications to the original loan or lease contract are carried forward as a part of the net investment in the new loan or lease. For troubled debt restructurings, all fees received in connection with a modification of terms are applied as a reduction of the loan or lease and any related costs, including direct loan origination costs, are charged to expense as incurred.

The Corporation purchased an individual loan in 2013 and a group of loans in connection with the Alterra acquisition which have shown evidence of credit deterioration since origination. These purchased loans are recorded at fair value, such that there is no carryover of the seller’s allowance for loan losses. Such purchased loans are accounted for individually. At acquisition, the Corporation estimates the amount and timing of expected cash flows for each purchased loan and the expected cash flows in excess of fair value are recorded as interest income over the remaining life of the loan (accretable yield). The excess of the loan’s contractual principal and interest over expected cash flows at acquisition is not recorded (nonaccretable difference).

Over the life of the loan, expected cash flows continue to be estimated. If the present value of expected cash flows is less than the carrying amount, losses are recognized by an increase in the allowance for loan losses. If the present value of expected cash flows is greater than the carrying amount, it is recognized as part of future interest income.

Allowance for Loan and Lease Losses

To determine the level and composition of the allowance for loan and lease losses, the Corporation categorizes the portfolio into segments with similar risk characteristics. First, the Corporation evaluates loans and leases for potential impairment classification. The Corporation analyzes each loan and lease determined to be impaired on an individual basis to determine a specific reserve based upon the estimated value of the underlying collateral for collateral-dependent loans, or alternatively, the present value of expected cash flows. The Corporation applies historical trends from established risk factors to each category of loans and leases that has not been individually evaluated for the purpose of establishing the general portion of the allowance.

Net Investment in Direct Financing Leases and Operating Leases

Net Investment in Direct Financing Leases. The net investment in direct financing lease agreements represents total undiscounted payments plus estimated unguaranteed residual value (approximating 3% to 20% of the cost of the related equipment) and is recorded as lease receivables when the lease is signed and the leased property is delivered to the client. The excess of the minimum lease payments and residual values over the cost of the equipment is recorded as unearned lease income. Unearned lease income is recognized over the term of the lease on a basis which results in an approximate level rate of return on the unrecovered lease investment. Lease payments are recorded when due under the lease contract. Residual values are established at lease inception equal to the estimated value to be received from the equipment following termination of the initial lease and such estimated value considers all relevant information and circumstances regarding the equipment. In estimating the equipment’s fair value at lease termination, the Corporation relies on internally or externally prepared appraisals, published sources of used equipment prices and historical experience adjusted for known current industry and economic trends. The Corporation’s estimates are periodically reviewed to ensure reasonableness; however, the amounts the Corporation will ultimately realize could differ from the estimated amounts. When there are other than temporary declines in the Corporation’s carrying amount of the unguaranteed residual value, the carrying value is reduced and charged to non-interest expense.

Operating Leases. Machinery and equipment are leased to clients under operating leases and are recorded at cost. Equipment under such leases is depreciated over the estimated useful life or term of the lease, if shorter. The impairment loss, if any, would be charged to expense in the period it becomes evident. Rental income is recorded on the straight-line accrual basis as other non-interest income.

Leasehold Improvements and Equipment

Premises and Equipment, net. The cost of buildings and capitalized leasehold improvements is amortized on the straight-line method over the lesser of the term of the respective lease or estimated economic life. Equipment is stated at cost less accumulated depreciation and amortization which is calculated by the straight-line method over the estimated useful lives of three to ten years. Maintenance and repair costs are charged to expense as incurred. Improvements which extend the useful life are capitalized and depreciated over the remaining useful life of the assets.

Foreclosed Properties

Foreclosed Properties. Property acquired by repossession, foreclosure or by deed in lieu of foreclosure is carried at the lower of the recorded investment in the loan at the time of acquisition or the fair value of the underlying property, less costs to sell. Any write-down in the carrying value of a loan or lease at the time of acquisition is charged to the allowance for loan and lease losses. Any subsequent write-downs to reflect current fair value, as well as gains and losses on disposition and revenues are recorded in non-interest expense. Costs relating to the development and improvement of the property are capitalized while holding period costs are charged to other non-interest expense.

Bank-Owned Life Insurance

Bank-Owned Life Insurance. Bank-owned life insurance (“BOLI”) is reported at the amount that would be realized if the life insurance policies were surrendered on the balance sheet date. BOLI policies owned by the Bank are purchased with the objective to fund certain future employee benefit costs with the death benefit proceeds. The cash surrender value of such policies is recorded in bank-owned life insurance on the Consolidated Balance Sheets and changes in the value are recorded in non-interest income. The total death benefit of all BOLI policies was $97.7 million and $97.3 million as of December 31, 2017 and 2016, respectively. There are no restrictions on the use of BOLI proceeds nor are there any contractual restrictions on the ability to surrender the policy. As of each of December 31, 2017 and 2016, there were no borrowings against the cash surrender value of the BOLI policies.

Regulatory Required Holdings

Federal Home Loan Bank and Federal Reserve Bank Stock. The Bank is required to maintain Federal Home Loan Bank (“FHLB”) stock as members of the FHLB, and in amounts as required by these institutions. Alterra, previously as a state chartered member of the Federal Reserve Bank of Kansas City, was required to own shares of Federal Reserve Bank (“FRB”) stock. These equity securities are “restricted” in that they can only be sold back to the respective institutions or another member institution at par. Therefore, they are less liquid than other marketable equity securities and their fair value is equal to cost. At December 31, 2017 and 2016, the Bank had FHLB stock of $1.1 million and $1.8 million, respectively. Alterra had FRB stock of $1.1 million at December 31, 2016. The Corporation periodically evaluates its holding in FHLB and FRB stock for impairment. Should the stock be impaired, it would be written down to its estimated fair value. There were no impairments recorded on FHLB and FRB stock during the year ended December 31, 2017 or 2016.

Goodwill and Intangible Assets

Goodwill and Other Intangible Assets. Goodwill and other intangible assets consist primarily of goodwill, core deposit intangibles and loan servicing rights. Core deposit intangibles have estimated finite lives and are amortized on an accelerated basis to expense over a period of seven years. Loan servicing rights, when purchased, are initially recorded at fair value and subsequently amortized in proportion to and over the period of estimated net servicing income. The Corporation reviews other intangible assets for impairment at least annually, or whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, in which case an impairment charge would be recorded.

Goodwill is not amortized but is subject to impairment tests on at least an annual basis, and more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount (including goodwill). An initial qualitative evaluation is made to assess the likelihood of impairment and determine whether further quantitative testing to calculate the fair value is necessary. When the qualitative evaluation indicates that impairment is more likely than not, quantitative testing is required whereby the fair value of each reporting unit is calculated and compared to the recorded book value, “step one.” If the calculated fair value of the reporting unit exceeds its carrying value, goodwill is not considered impaired and “step two” is not considered necessary. If the carrying value of a reporting unit exceeds its calculated fair value, the impairment test continues (“step two”) by comparing the carrying value of the reporting unit’s goodwill to the implied fair value of goodwill. The implied fair value is computed by adjusting all assets and liabilities of the reporting unit to current fair value with the offset adjustment to goodwill. The adjusted goodwill balance is the implied fair value of the goodwill. An impairment charge is recognized if the carrying value of goodwill exceeds the implied fair value of goodwill. See Note 6 for additional information on goodwill and other intangible assets.

SBA Recourse Reserve [Policy Text Block]

SBA Recourse Reserve. The Corporation establishes SBA recourse reserves on the guaranteed portions of sold SBA loans when it is probable that the guarantee may be ineligible. The recourse reserve is reported in accrued interest payable and other liabilities on the Consolidated Balance Sheets and consists of two components: (1) specific reserves for individually evaluated impaired loans that present a collateral shortfall where the guaranty associated with the sold portion of the SBA loan is determined to most likely be ineligible; and (2) general reserves for estimated probable losses on the remaining sold portfolio. The general reserve methodology is based on the evaluation of several factors, including but not limited to: credit quality trends within the SBA portfolio, changes in underlying collateral and the Corporation’s ability to originate, fund or service sold SBA loans in accordance with SBA regulations.

In the ordinary course of business, the Corporation sells the guaranteed portions of SBA loans to third parties. The Corporation has a continuing involvement in each of the transferred lending arrangements by way of relationship management, servicing the loans, as well as being subject to normal and customary requirements of the SBA loan program; however, there are no further obligations to the third-party participant required of the Corporation, other than standard representations and warranties related to sold amounts. In the event of a loss resulting from default and a determination by the SBA that there is a deficiency in the manner in which the loan was originated, funded or serviced by the Corporation, the SBA may require the Corporation to repurchase the loan, deny its liability under the guaranty, reduce the amount of the guaranty, or, if it has already paid under the guaranty, seek recovery of the principal loss related to the deficiency from the Corporation. The Corporation must comply with applicable SBA regulations in order to maintain the guaranty. In addition, the Corporation retains the option to repurchase the sold guaranteed portion of an SBA loan if the loan defaults. See Note 18 for additional information on the SBA recourse reserve.

Other Investments

Other Investments. The Corporation owns certain equity investments in other corporate organizations which are not consolidated because the Corporation does not own more than a 50% interest or exercise control over the organization. Investments in corporations representing at least a 20% interest are generally accounted for using the equity method and investments in corporations representing less than 20% interest are generally accounted for at cost. Investments in limited partnerships representing from at least a 3% up to a 50% interest in the entity are generally accounted for using the equity method and investments in limited partnerships representing less than 3% are generally accounted for at cost. All of these investments are periodically evaluated for impairment. Should an investment be impaired, it would be written down to its estimated fair value. The equity investments are reported in other assets and the income and expense from such investments, if any, is reported in non-interest income and non-interest expense.

Derivative Instruments

Derivative Instruments. The Corporation uses derivative instruments to protect against the risk of adverse price or interest rate movements on the value of certain assets, liabilities, future cash flows and economic hedges for written client derivative contracts. Derivative instruments represent contracts between parties that usually require little or no initial net investment and result in one party delivering cash to the other party based on a notional amount and an underlying variable, as specified in the contract, and may be subject to master netting agreements.

Market risk is the risk of loss arising from an adverse change in interest rates, exchange rates or equity prices. The Corporation’s primary market risk is interest rate risk. Instruments designed to manage interest rate risk include interest rate swaps, interest rate options and interest rate caps and floors with indices that relate to the pricing of specific assets and liabilities. The nature and volume of the derivative instruments used to manage interest rate risk depend on the level and type of assets and liabilities on the balance sheet and the risk management strategies for the current and anticipated rate environments. Counterparty risk with respect to derivative instruments occurs when a counterparty to a derivative contract with an unrealized gain fails to perform according to the terms of the agreement. Counterparty risk is managed by limiting the counterparties to highly rated dealers, requiring collateral postings when values are in deficit positions, applying uniform credit standards to all activities with credit risk and monitoring the size and the maturity structure of the derivative portfolio.

All derivative instruments are to be carried at fair value on the Consolidated Balance Sheets. The accounting for the gain or loss due to changes in the fair value of a derivative instrument depends on whether the derivative instrument qualifies as a hedge. If the derivative instrument does not qualify as a hedge, the gains or losses are reported in earnings when they occur. However, if the derivative instrument qualifies as a hedge, the accounting varies based on the type of risk being hedged. In 2017 and 2016, the Corporation utilized interest rate swaps offered directly to qualified commercial borrowers, which did not qualify for hedge accounting, and therefore, all changes in fair value and gains and losses on these instruments were reported in earnings as they occurred. The effects of netting arrangements are disclosed within the Notes of the Consolidated Financial Statements.

Income Taxes

Income Taxes. Deferred income tax assets and liabilities are computed for temporary differences in timing between the financial statement and tax basis of assets and liabilities that result in taxable or deductible amounts in the future based on enacted tax law and rates applicable to periods in which the differences are expected to affect taxable income. The effect of a change in tax rates on deferred taxes is recognized in income in the period that includes the enactment date. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversals of deferred tax liabilities, appropriate tax planning strategies and projections for future taxable income over the period which the deferred tax assets are deductible. When necessary, valuation allowances are established to reduce deferred tax assets to the realizable amount. Management believes it is more likely than not that the Corporation will realize the benefits of these deductible differences, net of the existing valuation allowances.

Income tax expense or benefit represents the tax payable or tax refundable for a period, adjusted by the applicable change in deferred tax assets and liabilities for that period. The Corporation also invests in certain development entities that generate federal and state historic tax credits. The tax benefits associated with these investments are accounted for under the flow-through method and are recognized when the respective project is placed in service. The Corporation and its subsidiaries file a consolidated federal income tax return and separate state income tax returns. Tax sharing agreements allocate taxes to each legal entity for the settlement of intercompany taxes. The Corporation applies a more likely than not standard to each of its tax positions when determining the amount of tax expense or benefit to record in its financial statements. Unrecognized tax benefits are recorded in other liabilities. The Corporation recognizes accrued interest relating to unrecognized tax benefits in income tax expense and penalties in other non-interest expense.

Comprehensive Income

Other Comprehensive Income or Loss. Comprehensive income or loss, shown as a separate financial statement, includes net income or loss, changes in unrealized holding gains and losses on available-for-sale securities, changes in deferred gains and losses on investment securities transferred from available-for-sale to held-to-maturity, if any, changes in unrealized gains and losses associated with cash flow hedging instruments, if any, and the amortization of deferred gains and losses associated with terminated cash flow hedges, if any. For the year ended December 31, 2017, realized securities losses of $403,000 were reclassified out of accumulated other comprehensive income. Realized securities gains of $10,000 were reclassified out of accumulated other comprehensive income for the year ended December 31, 2016.

Earnings Per Share

Earnings Per Common Share. Earnings per common share (“EPS”) is computed using the two-class method. Basic EPS is computed by dividing net income allocated to common shares by the weighted average number of common shares outstanding for the period, excluding any participating securities. Participating securities include unvested restricted shares. Unvested restricted shares are considered participating securities because holders of these securities receive non-forfeitable dividends at the same rate as the holders of the Corporation’s common stock. Diluted EPS is computed by dividing net income allocated to common shares adjusted for reallocation of undistributed earnings of unvested restricted shares by the weighted average number of common shares determined for the basic EPS plus the dilutive effect of common stock equivalents using the treasury stock method based on the average market price for the period.

Segments and Related Information

Segments and Related Information. The Corporation is required to report each operating segment based on materiality thresholds of ten percent or more of certain amounts, such as revenue. Additionally, the Corporation is required to report separate operating segments until the revenue attributable to such segments is at least 75 percent of total consolidated revenue. The Corporation provides a broad range of financial services to individuals and companies in the Midwest. These services include demand, time and savings products, the sale of certain non-deposit financial products and commercial and retail lending, leasing and trust services. While the Corporation’s chief decision-maker monitors the revenue streams of the various products, services and locations, operations are managed and financial performance is evaluated on a corporate-wide basis. The Corporation’s business units have similar basic characteristics in the nature of the products, production processes and type or class of client for products or services; therefore, these business units are considered one operating segment.

Stock Options

Restricted Stock

Under the Plan, the Corporation may grant restricted stock to plan participants, subject to forfeiture upon the occurrence of certain events until the dates specified in the participant’s award agreement. While restricted stock is subject to forfeiture, restricted stock participants may exercise full voting rights and will receive all dividends and other distributions paid with respect to the restricted shares. Restricted stock units do not have voting rights and are provided dividend equivalents. The restricted stock granted under the Plan is typically subject to a vesting period. Compensation expense is recognized over the requisite service period of generally four years for the entire award on a straight-line basis. Upon vesting of restricted stock, the benefit of tax deductions in excess of recognized compensation expense is reflected as an income tax benefit in the Consolidated Statements of Income.

Future Accounting Changes

Recent Accounting Pronouncements.

In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” with an original effective date for annual reporting periods beginning after December 15, 2016. The ASU is a converged standard between the FASB and the IASB that provides a single comprehensive revenue recognition model for all contracts with customers across transactions and industries. The primary objective of the ASU is revenue recognition that represents the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU No. 2015-14, which defers the effective date of ASU 2014-09 to annual and interim reporting periods in fiscal years beginning after December 15, 2017. Earlier application is permitted only as of annual and interim reporting periods in fiscal years beginning after December 15, 2016. In March 2016, the FASB issued ASU No. 2016-08, “Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net.” The ASU intends to improve the operability and understandability of the implementation guidance of ASU 2014-09 on principal versus agent considerations. In April, May and December 2016, the FASB also issued ASU No. 2016-10, No. 2016-12 and No. 2016-20, respectively, related to Topic 606. The amendments do not change the core principals of the previously issued guidance, but instead further clarify and provide implementation guidance for certain aspects of the original ASU. The Corporation intends to adopt the accounting standards during the first quarter of 2018, as required. The Corporation conducted its assessment of the primary contracts subject to the guidance, including trust and asset management fees, brokerage commissions and deposit service charges. The Corporation has concluded that the adoption of the accounting standard will not have a material impact on the Corporation’s existing revenue recognition practices or on its results of operations, financial position and liquidity.

In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842).” The ASU intends to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities and disclosing key information about leasing arrangements. The ASU will require lessees to recognize the following for all leases (with the exception of short-term leases) at the commencement date: (1) a lease liability, which is a lessees’ obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Under the new guidance, lessor accounting is largely unchanged. Certain targeted improvements were made to align, where necessary, lessor accounting with the lessee accounting model and Topic 606, Revenue from Contracts with Customers. The new lease guidance simplifies the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. The ASU is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Corporation intends to adopt the accounting standard during the first quarter of 2019, as required, and is currently evaluating the impact on its results of operations, financial position and liquidity.

In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments- Credit Losses (Topic 326).” The ASU replaces the incurred loss impairment methodology for recognizing credit losses with a methodology that reflects all expected credit losses. The ASU also requires consideration of a broader range of information to inform credit loss estimates, including such factors as past events, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. The amendments affect loans, debt securities, trade receivables, net investments in leases, off-balance-sheet credit exposures, and any other financial asset not excluded from the scope that have the contractual right to receive cash. Entities will apply the amendments in the ASU through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. The ASU is effective for public companies for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted as of the fiscal years beginning after December 15, 2018. The Corporation intends to adopt the accounting standard during the first quarter of 2020, as required, and is currently evaluating the impact on its results of operations, financial position and liquidity. A cross-functional team has been established to assess and implement the standard.

In May 2017, the FASB issued ASU No. 2017-09, “Compensation- Stock Compensation (Topic 718).” The ASU provides clarity about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The ASU is effective for all entities for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. The Corporation is in the process of evaluating the impact of this standard but does not expect this standard to have a material impact on its results of operations, financial position and liquidity.

In August 2017, the FASB issued ASU No. 2017-12, “Derivatives and Hedging (Topic 815).” The ASU intends to better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. It also expands and refines hedge accounting for both nonfinancial and financial risk components and aligns the recognition and presentation of the effects of the hedging instrument and the hedged item. The ASU is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The Corporation adopted the standard in the fourth quarter of 2017 with no material impact on its results of operations, financial position and liquidity.