| Summary of Significant Accounting Policies (Policies) | 12 Months Ended |
| Dec. 31, 2014 |
| Accounting Policies [Abstract] | |
| Principles of Consolidation | | (a) | Principles of Consolidation |
| The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary Wilson Bank. All significant intercompany accounts and transactions have been eliminated in consolidation. |
| Nature of Operations | | (b) | Nature of Operations |
| Wilson Bank operates under a state bank charter and provides full banking services. As a state-chartered bank that is not a member of the Federal Reserve, Wilson Bank is subject to regulations of the Tennessee Department of Financial Institutions and the Federal Deposit Insurance Corporation (“FDIC”). The areas served by Wilson Bank include Wilson County, DeKalb County, Rutherford County, Smith County, Trousdale County, Sumner County, and eastern Davidson County, Tennessee and surrounding counties in Middle Tennessee. Services are provided at the main office and twenty-four branch locations. |
| Estimates | | (c) | Estimates |
| In preparing consolidated financial statements in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”), management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term relate to the determination of the allowance for loan losses, the valuation of deferred tax assets, other-than-temporary impairments of securities, and the fair value of financial instruments. |
| Significant Group Concentrations of Credit Risk | | (d) | Significant Group Concentrations of Credit Risk |
| Most of the Company’s activities are with customers located within Middle Tennessee. The types of securities in which the Company invests are described in note 3. The types of lending in which the Company engages are described in note 2. The Company does not have any significant concentrations to any one industry or customer other than as disclosed in note 2. |
| Residential 1-4 family, commercial real estate and construction mortgage loans, represented 26%, 42% and 18% and 28%, 44% and 16% of the loan portfolio at December 31, 2014 and 2013, respectively. |
| Loans | (e) | Loans | |
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| The Company grants mortgage, commercial and consumer loans to customers. A substantial portion of the loan portfolio is represented by mortgage loans throughout Middle Tennessee. The ability of the Company’s debtors to honor their contracts is dependent upon the real estate and general economic conditions in this area. |
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| Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off generally are reported at their outstanding unpaid principal balances adjusted for unearned income, the allowance for loan losses, and any unamortized deferred fees or costs on originated loans, and premiums or discounts on purchased loans. |
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| Loan origination fees, net of certain direct origination costs, as well as premiums and discounts, are deferred and amortized on a straight line basis over the respective term of the loan. |
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| As part of our routine credit monitoring process, the Company performs regular credit reviews of the loan portfolio and loans receive risk ratings by the assigned credit officer, which are subject to validation by our independent loan review department. Risk ratings are categorized as pass, special mention, substandard or doubtful. The Company believes that our categories follow those outlined by our primary regulator. |
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| Generally the accrual of interest on mortgage and commercial loans is discontinued at the time the loan is 90 days past due unless the credit is well-secured and in process of collection. Credit card loans and other personal loans are typically charged off no later than when they become 180 days past due. Past due status is based on contractual terms of the loan. In all cases, loans are placed on nonaccrual or charged-off at an earlier date if collection of principal or interest is considered doubtful. |
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| All interest accrued but not collected for loans that are placed on nonaccrual or charged off is reversed against interest income. The interest on these loans is accounted for on the cash-basis or cost-recovery method, until qualifying for return to accrual. Loans are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured. |
| Allowance for Loan Losses | (f) | Allowance for Loan Losses | |
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| Management provides for loan losses by establishing an allowance. The allowance for loan losses is established as losses are estimated to have occurred through a provision for loan losses charged to earnings. Loan losses are charged against the allowance when management believes the uncollectibility of a loan balance is confirmed. Subsequent recoveries, if any, are credited to the allowance. |
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| The allowance for loan losses is evaluated on a monthly basis by management and is based upon management’s monthly review of the collectibility of the loans in light of historical experience, the nature and volume of the loan portfolio, adverse situations that may affect the borrower’s ability to repay, estimated value of any underlying collateral and prevailing economic conditions. This evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available. |
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| In assessing the adequacy of the allowance, we also consider the results of our ongoing independent loan review process. We undertake this process both to ascertain whether there are loans in the portfolio whose credit quality has weakened over time and to assist in our overall evaluation of the risk characteristics of the entire loan portfolio. Our loan review process includes the judgment of management, independent loan reviewers, and reviews that may have been conducted by third-party reviewers. We incorporate relevant loan review results in the loan impairment determination. In addition, regulatory agencies, as an integral part of their examination process, will periodically review the Company’s allowance for loan losses and may require the Company to record adjustments to the allowance based on their judgment about information available to them at the time of their examinations. |
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| In addition to the independent loan review process, the aforementioned risk ratings are subject to continual review by the loan officer to determine that the appropriate risk ratings are being utilized in our allowance for loan loss process. Each risk rating is also subject to review by our independent loan review department. Currently, our independent loan review department targets reviews of 100% of existing loan relationships with aggregate debt of $1.0 million and greater and new loans with aggregate debt of $500,000 and greater. In addition, loan review targets portfolio segments, loans assigned to a particular lending officer, and loans with four or more renewals. |
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| The allowance consists of allocated and general components. The allocated component relates to loans that are classified as impaired. For those loans that are individually classified as impaired, an allowance is established when the discounted cash flows (or collateral value or observable market price) of the impaired loan is lower than the carrying value of that loan. The general component covers nonclassified loans and is based on historical charge-off experience and other adjustments based on management’s assessment of internal or external influences on credit quality that are not fully reflected in the historical loss or risk rating data. |
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| A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. Factors considered by management in determining impairment include payment status, collateral value, and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of the delay, the reasons for the delay, the borrower’s prior payment record, and the amount of the shortfall in relation to the principal and interest owed. Impairment is measured on a loan by loan basis for commercial, mortgage and agricultural loans by either the present value of expected future cash flows discounted at the loan’s effective interest rate, the loan’s obtainable market price, or the fair value of the collateral if the loan is collateral dependent. |
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| Large groups of smaller balance homogeneous loans are collectively evaluated for impairment. Accordingly, the Company does not separately identify individual consumer loans for impairment disclosures, unless such loans are the subject of a restructuring agreement due to financial difficulties of the borrower. |
| Debt and Equity Securities | | (g) | Debt and Equity Securities |
| Certain debt securities that management has the positive intent and ability to hold to maturity are classified as “held to maturity” and recorded at amortized cost. Trading securities are recorded at fair value with changes in fair value included in earnings. Securities not classified as held to maturity or trading, including equity securities with readily determinable fair values, are classified as “available for sale” and recorded at fair value based on available market prices, with unrealized gains and losses excluded from earnings and reported in other comprehensive income on an after-tax basis. Securities classified as “available for sale” are held for indefinite periods of time and may be sold in response to movements in market interest rates, changes in the maturity or mix of Company assets and liabilities or demand for liquidity. Purchase premiums and discounts are recognized in interest income using the interest method over the terms of the securities. Gains and losses on the sale of securities are recorded on the trade date and are determined using the specific identification method. |
| Other-than-temporary Impairment—Impaired securities are assessed quarterly for the presence of other-than-temporary impairment (“OTTI”). A decline in the fair value of any available-for-sale or held-to-maturity security below cost that is deemed to be other-than-temporary results in a reduction in the carrying amount of the security. To determine whether OTTI has occurred, management considers factors such as (1) length of time and extent that fair value has been less than cost, (2) the financial condition and near term prospectus of the issuer, and (3) the Bank’s ability and intent to hold the security for a period sufficient to allow for any anticipated recovery in fair value. If management deems a security to be OTTI, management reviews the present value of the future cash flows associated with the security. A shortfall of the present value of the cash flows expected to be collected in relation to the amortized cost basis is referred to as a credit loss. If a credit loss is identified, the credit loss is recognized as a charge to earnings and a new cost basis for the security is established. If management concludes that no credit loss exists and it is not “more-likely-than-not” that it will be required to sell the security before the recovery of the security’s cost basis, then the security is not deemed OTTI and the shortfall is recorded as a component of equity. |
| No securities have been classified as trading securities. |
| Federal Home Loan Bank Stock | | (h) | Federal Home Loan Bank Stock |
| The Company, as a member of the Federal Home Loan Bank (“FHLB”) Cincinnati system, is required to maintain an investment in capital stock of the FHLB. Based on redemption provisions of the FHLB, the stock has no quoted market value and is carried at par value, which approximates its fair value. Management reviews the investment for impairment based on the ultimate recoverability of the cost basis in the FHLB stock. As of December 31, 2014, the minimum required investment was approximately $2,600,000. Stock redemptions are at the discretion of the FHLB. |
| Loans Held for Sale | | (i) | Loans Held for Sale |
| Loans originated and intended for sale in the secondary market are carried at the lower of cost or fair value. For loans carried at lower of cost or fair value, gains and losses on loans sales (sales proceeds minus carrying value) are recorded in non-interest income, and direct loan origination costs and fees are deferred at origination of the loan and are recognized in non-interest income upon sale of the loan. |
| Premises and Equipment | | (j) | Premises and Equipment |
| Premises and equipment are stated at cost. Depreciation is computed primarily by the straight-line method over the estimated useful lives of the related assets. Gains or losses realized on items retired and otherwise disposed of is credited or charged to operations and cost and related accumulated depreciation are removed from the asset and accumulated depreciation accounts. |
| Expenditures for major renovations and improvements of premises and equipment are capitalized and those for maintenance and repairs are charged to earnings as incurred. |
| Other Real Estate | | (k) | Other Real Estate |
| Assets acquired through, or in lieu of, loan foreclosure are held for sale and are initially recorded at fair value less the estimated cost to sell at the date of foreclosure, establishing a new cost basis. Subsequent to their acquisition by the Company, valuations of these assets are periodically performed by management, and the assets are carried at the lower of carrying amount or fair value less cost to sell. Revenue and expenses from operations and changes in the valuation allowance [i.e. any direct write-downs] are included in net expenses from foreclosed assets. |
| Intangible Assets | | (l) | Intangible Assets |
| The Financial Accounting Standards Board “FASB” Accounting Standards Codification “ASC” 350, Goodwill and Other Intangible Assets (“ASC 350”) requires that management determine the allocation of intangible assets into identifiable groups at the date of acquisition and that appropriate amortization periods be established. Under the provisions of FASB ASC 350, goodwill is not to be amortized; rather, it is to be monitored for impairment and written down to the impairment value at the time impairment occurs. The Company has determined that no impairment loss needs to be recognized related to its goodwill. |
| Cash and Cash Equivalents | | (m) | Cash and Cash Equivalents |
| For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks and Federal funds sold. Generally, Federal funds sold are purchased and sold for one-day periods. Management makes deposits only with financial institutions it considers to be financially sound. |
| Long-Term Assets | | (n) | Long-Term Assets |
| Premises and equipment, intangible assets, and other long-term assets are reviewed for impairment when events indicate their carrying amount may not be recoverable from future undiscounted cash flows. If impaired, the assets are recorded at fair value. |
| Securities Sold Under Agreements to Repurchase | | (o) | Securities Sold Under Agreements to Repurchase |
| Substantially all repurchase agreement liabilities represent amounts advanced by various customers. Securities are pledged to cover these liabilities, which are not covered by Federal deposit insurance. |
| Income Taxes | | (p) | Income Taxes |
| The Company accounts for Income Taxes in accordance with income tax accounting guidance (FASB ASC 740, Income Taxes). The Company follows accounting guidance related to accounting for uncertainty in income taxes, which sets out a consistent framework to determine the appropriate level of tax reserves to maintain for uncertain tax positions. |
| The income tax accounting guidance results in two components of income tax expense: current and deferred. Current income tax expense reflects taxes to be paid or refunded for the current period by applying the provisions of the enacted tax law to the taxable income or excess of deductions over revenues. The Company determines deferred income taxes using the liability (or balance sheet) method. Under this method, the net deferred tax asset or liability is based on the tax effects of the differences between the book and tax bases of assets and liabilities, and enacted changes in tax rates and laws are recognized in the period in which they occur. |
| Deferred income tax expense results from changes in deferred tax assets and liabilities between periods. Deferred tax assets are recognized if it is more likely than not, based on the technical merits, that the tax position will be realized or sustained upon examination. The term more likely than not means a likelihood of more than 50 percent; the terms examined and upon examination also include resolution of the related appeals or litigation processes, if any. A tax position that meets the more-likely-than-not recognition threshold is initially and subsequently measured as the largest amount of tax benefit that has a greater than 50 percent likelihood of being realized upon settlement with a taxing authority that has full knowledge of all relevant information. The determination of whether or not a tax position has met the more-likely-than-not recognition threshold considers the facts, circumstances, and information available at the reporting date and is subject to management’s judgment. Deferred tax assets are reduced by a valuation allowance if, based on the weight of evidence available, it is more likely than not that some portion or all of a deferred tax asset will not be realized. |
| The Company recognizes interest and penalties on income taxes as a component of income tax expense. |
| Stock Options | | (q) | Stock Options |
| Stock compensation accounting guidance (FASB ASC 718, “Compensation—Stock Compensation”) requires that the compensation cost relating to share-based payment transactions be recognized in financial statements. That cost will be measured based on the grant date fair value of the equity or liability instruments issued. The stock compensation accounting guidance covers a wide range of share-based compensation arrangements including stock options, restricted share plans, performance-based awards, share appreciation rights, and employee share purchase plans. |
| The stock compensation accounting guidance requires that compensation cost for all stock awards be calculated and recognized over the employees’ service period, generally defined as the vesting period. For awards with graded-vesting, compensation cost is recognized on a straight-line basis over the requisite service period for the entire award. The Company uses the Black-Scholes option pricing model to estimate the fair value of stock options. |
| Advertising Costs | | (r) | Advertising Costs |
| Advertising costs are expensed as incurred by the Company and totaled $1,884,000, $2,104,000 and $1,230,000 for 2014, 2013 and 2012, respectively. |
| Earnings Per Share | | (s) | Earnings Per Share |
| Basic earnings per share represents income available to common stockholders divided by the weighted-average number of common shares outstanding during the period. Diluted earnings per share reflects additional potential common shares that would have been outstanding if dilutive potential common shares had been issued, as well as any adjustment to income that would result from the assumed issuance. Potential common shares that may be issued by the Company relate solely to outstanding stock options and are determined using the treasury stock method. |
| Fair Value of Financial Instruments | | (t) | Fair Value of Financial Instruments |
| Fair values of financial instruments are estimated using relevant market information and other assumptions, as more fully disclosed in note 20 of the consolidated financial statements. Fair value estimates involve uncertainties and matters of significant judgment. Changes in assumptions or in market conditions could significantly affect the estimates. |
| Reclassifications | | (u) | Reclassifications |
| Certain reclassifications have been made to the 2013 and 2012 figures to conform to the presentation for 2014. |
| Off-Balance-Sheet Financial Instruments | | (v) | Off-Balance-Sheet Financial Instruments |
| In the ordinary course of business Wilson Bank, has entered into off-balance-sheet financial instruments consisting of commitments to extend credit, commitments under credit card arrangements, commercial letters of credit and standby letters of credit. Such financial instruments are recorded in the financial statements when they are funded or related fees are incurred or received. |
| Recently Adopted Accounting Pronouncements | | (w) | Recently Adopted Accounting Pronouncements |
| In February 2013, the FASB issued ASU No. 2013-02, “Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income” which provides disclosure guidance on amounts reclassified out of Accumulated Other Comprehensive Income by component. The adoption of this ASU did not have any impact on the Company’s financial position or results of operations but has impacted our financial statement disclosure. As shown on the statement of comprehensive earnings for the three years ended December 31, 2014, the Company reclassified approximately $336,000, $48,000 and $160,000 of net gains out of other comprehensive earnings into gain on the sale of investment securities, net of tax. |
| In January 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-04, Receivables—Troubled Debt Restructurings by Creditors (Subtopic 310-40); Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans Upon Foreclosure, to reduce the diversity in reporting when an in substance repossession or foreclosure occurs, that is, when a creditor should be considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan such that the loan receivable should be derecognized and the real estate property recognized. The amendments in this ASU clarify that an in substance repossession or foreclosure occurs, and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan upon either (1) the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or (2) the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure or through a similar legal agreement. Additionally, the amendments require interim and annual disclosure of both (1) the amount of foreclosed residential real estate property held by the creditor and (2) the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure according to local requirements of the applicable jurisdiction. The Company adopted this ASU in the first quarter of 2014 using the prospective method and had one loan that met the above stated criteria as of December 31, 2014 totaling $279,000. The total amount of foreclosed residential real property amounted to $456,000 at December 31, 2014. |
| There were no other recently issued accounting pronouncements that are expected to materially impact the Company. |
| Fair Value Measurements and Disclosures | FASB ASC 820, Fair Value Measurements and Disclosures (“ASC 820”), which defines fair value, establishes a framework for measuring fair value in U.S. GAAP and expands disclosures about fair value measurements. The definition of fair value focuses on the exit price, i.e., the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, not the entry price, i.e., the price that would be paid to acquire the asset or received to assume the liability at the measurement date. The statement emphasizes that fair value is a market-based measurement; not an entity-specific measurement. Therefore, the fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. |
