Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2022
Accounting Policies [Abstract]
Nature of Business [Policy Text Block]	Nature of Business — Wilson Bank Holding Company (the “Company”) is a bank holding company whose primary business is conducted by its wholly-owned subsidiary, Wilson Bank & Trust (the “Bank”). The Bank is a commercial bank headquartered in Lebanon, Tennessee. The Bank provides a full range of banking services in its primary market areas of Wilson, Davidson, Rutherford, Trousdale, Sumner, Dekalb, Putnam, Smith, and Williamson Counties, Tennessee. On June 1, 2022, the Bank began operations with a newly-formed joint venture, Encompass Home Lending, LLC ("Encompass") of which the Bank owns 51% of the outstanding membership interests. Encompass offers residential mortgage banking services to customers of certain home builders in our markets.
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation — The accompanying unaudited, consolidated financial statements have been prepared in accordance with instructions to Form 10-Q and therefore do not include all information and footnotes necessary for a fair presentation of financial position, results of operations, and cash flows in conformity with U.S. generally accepted accounting principles. All adjustments consisting of normally recurring accruals that, in the opinion of management, are necessary for a fair presentation of the financial position and results of operations for the periods covered by the report have been included. The accompanying unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated audited financial statements and related notes appearing in the Company's Annual Report on Form 10-K for the year ended December 31, 2021. These consolidated financial statements include the accounts of the Company, the Bank, and Encompass. Significant intercompany transactions and accounts are eliminated in consolidation.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates — The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the balance sheet date and the 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 include the determination of the allowance for credit losses, the valuation of deferred tax assets, determination of any impairment of goodwill or other intangibles, the valuation of other real estate (if any), and the fair value of financial instruments. These financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2021. There have been no significant changes to the Company’s significant accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021 other than the adoption of ASC 326 as described in Note 1. Summary of Significant Accounting Policies - Accounting Changes, Reclassifications and Restatements and in Note 2 - Loans and Allowance for Credit Losses.
Accounting Changes, Reclassifications and Restatements [Policy Text Block]	Accounting Changes, Reclassifications and Restatements – Certain items in prior financial statements have been reclassified to conform to the current presentation. In addition, on January 1, 2022, we adopted Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” as subsequently updated for certain clarifications, targeted relief and codification improvements. Accounting Standards Codification (“ASC”) Topic 326 (“ASC 326”) replaces the previous “incurred loss” model for measuring credit losses, which encompassed allowances for current known and inherent losses within the portfolio, with an “expected loss” model, which encompasses allowances for losses expected to be incurred over the life of the portfolio. The new current expected credit loss (“CECL”) model requires the measurement of all expected credit losses for financial assets measured at amortized cost and certain off-balance-sheet credit exposures based on historical experience, current conditions, and reasonable and supportable forecasts. ASC 326 also requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASC 326 includes certain changes to the accounting for available-for-sale securities including the requirement to present credit losses as an allowance rather than as a direct write-down for available-for-sale securities management does not intend to sell or believes that it is more likely than not they will be required to sell. We adopted ASC 326 using the modified retrospective method for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Upon adoption, we recognized an after-tax cumulative effect increase to retained earnings totaling $1.0 million. Operating results for periods after January 1, 2022 are presented in accordance with ASC 326 while prior period amounts continue to be reported in accordance with previously applicable standards and the accounting policies described in our 2021 Form 10-K. In connection with the adoption of ASC 326, we revised certain accounting policies and implemented certain accounting policy elections. The revised accounting policies are described below.
Financing Receivable, Allowance for Credit Losses, Policy for Uncollectible Amounts [Policy Text Block]	Allowance For Credit Losses - Loans — The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present management's best estimate of the net amount expected to be collected. Loans are charged-off against the allowance when deemed uncollectible by management. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management has made the accounting policy election to exclude accrued interest receivable on loans from the estimate of credit losses. Further information regarding our policies and methodology used to estimate the allowance for credit losses on loans is presented in Note 2 - Loans and Allowance for Credit Losses.
Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block]	Allowance For Credit Losses - Off-Balance-Sheet Credit Exposures — The allowance for credit losses on off-balance-sheet credit exposures is a liability account, calculated in accordance with ASC 326, representing expected credit losses over the contractual period for which we are exposed to credit risk resulting from a contractual obligation to extend credit. No allowance is recognized if we have the unconditional right to cancel the obligation. The allowance is reported as a component of accrued interest payable and other liabilities in our consolidated balance sheets. Adjustments to the allowance are reported in our income statement as a component of non-interest expense. Further information regarding our policies and methodology used to estimate the allowance for credit losses on off-balance-sheet credit exposures is presented in Note 11 - Commitments and Contingent Liabilities.
Investment, Policy [Policy Text Block]	Securities – Securities are classified as held to maturity and carried at amortized cost when management has the positive intent and ability to hold them until maturity. Securities to be held for indefinite periods of time are classified as available for sale and carried at fair value, with the unrealized holding gains and losses (those for which no allowance for credit losses are recorded) reported as a component of other comprehensive earnings, net of tax. Securities held for resale in anticipation of short-term market movements are classified as trading and are carried at fair value, with changes in unrealized holding gains and losses included in income. Management determines the appropriate classification of securities at the time of purchase. Securities with limited marketability, such as stock in the Federal Reserve Bank and the Federal Home Loan Bank, are carried at cost. Interest income on securities includes amortization of purchase premiums and discounts. Premiums and discounts on securities are generally amortized using the interest method with a constant effective yield without anticipating prepayments, except for mortgage-backed securities where prepayments are anticipated. Premiums on callable securities are amortized to their earliest call date. A security is placed on non-accrual status if (i) principal or interest has been in default for a period of 90 days or more or (ii) full payment of principal and interest is not expected. Interest accrued but not received for a security placed on non-accrual status is reversed against interest income. Gains and losses on sales are recorded on the trade date and are derived from the amortized cost of the security sold. Allowance for Credit Losses - Securities Available-for-Sale — For any securities classified as available-for-sale that are in an unrealized loss position at the balance sheet date, the Company assesses whether or not it intends to sell the security, or more likely than not will be required to sell the security, before recovery of its amortized cost basis. If either criteria is met, the security's amortized cost basis is written down to fair value through net income. If neither criteria is met, the Company evaluates whether any portion of the decline in fair value is the result of credit deterioration. Such evaluations consider the extent to which the amortized cost of the security exceeds its fair value, changes in credit ratings and any other known adverse conditions related to the specific security. If the evaluation indicates that a credit loss exists, an allowance for credit losses is recorded for the amount by which the amortized cost basis of the security exceeds the present value of cash flows expected to be collected, limited by the amount by which the amortized cost exceeds fair value. Any impairment not recognized in the allowance for credit losses is recognized in other comprehensive income.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Issued Accounting Pronouncements Information about certain recently issued accounting standards updates is presented below. Also refer to Note 1 - Accounting Standards Updates in our 2021 Form 10-K for additional information related to previously issued accounting standards updates. ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” In March 2020, the FASB issued this ASU and has issued subsequent amendments thereto, which provides temporary optional guidance to ease the potential burden in accounting for reference rate reform. The ASU provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued. It is intended to help stakeholders during the global market-wide reference rate transition period. The guidance is effective for all entities as of March 12, 2020 through December 31, 2022. The Company has implemented a transition plan to identify and modify its loans and other financial instruments with attributes that are either directly or indirectly influenced by LIBOR. The Company has discontinued originating LIBOR-based loans during 2022 and has begun negotiating loans primarily using its preferred replacement index, the Secured Overnight Financing Rate ("SOFR"). For the Company’s currently outstanding LIBOR-based loans, the timing and manner in which each customer's contract transitions to SOFR will vary on a case-by-case basis. The Company expects to complete all transitions by August 2023. ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. As noted above, effective January 1, 2022 the Company adopted ASU 2016-13, which resulted in a $7.6 million decrease to the allowance for credit losses and a $6.2 million increase to the reserve for unfunded commitments, resulting in a $1.0 million increase in retained earnings (net of taxes). See Note 2 – Loans and Allowance for Credit Losses for additional information. ASU 2022-01, “Derivatives and Hedging (Topic 815): Fair Value Hedging - Portfolio Layer Method.” ASU 2022-01 was issued to expand the scope of assets eligible for portfolio layer method hedging to include all financial assets. The update also expands the current last-of-layer method that permits only one hedged layer to allow multiple hedged layers of a single closed portfolio. The last-of-layer method is renamed the portfolio layer method, because more than the last layer of a portfolio could be hedged. The guidance is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2022. The adoption of ASU 2022-01 is not expected to have a significant impact on our financial statements. ASU 2022-02, “Financial Instruments - Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures.” ASU 2022-02 was issued to respond to feedback received from post-implementation review of Topic 326. The amendments eliminate the troubled debt restructuring (TDR) recognition and measurement guidance and now require that an entity evaluate whether the modification represents a new loan or a continuation of an existing loan. The amendments enhance existing disclosures and include new disclosure requirements related to certain modifications of receivables made to borrowers experiencing financial difficulty. To improve consistency for vintage disclosures, the ASU requires that public business entities disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases within the scope of Subtopic 326-20. The guidance is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2022. The adoption of ASU 2022-02 is not expected to have a significant impact on our financial statements. Other than those previously discussed, there were no other recently issued accounting pronouncements that are expected to materially impact the Company.

Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2022

Nature of Business — Wilson Bank Holding Company (the “Company”) is a bank holding company whose primary business is conducted by its wholly-owned subsidiary, Wilson Bank & Trust (the “Bank”). The Bank is a commercial bank headquartered in Lebanon, Tennessee. The Bank provides a full range of banking services in its primary market areas of Wilson, Davidson, Rutherford, Trousdale, Sumner, Dekalb, Putnam, Smith, and Williamson Counties, Tennessee. On June 1, 2022, the Bank began operations with a newly-formed joint venture, Encompass Home Lending, LLC ("Encompass") of which the Bank owns 51% of the outstanding membership interests. Encompass offers residential mortgage banking services to customers of certain home builders in our markets.

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation — The accompanying unaudited, consolidated financial statements have been prepared in accordance with instructions to Form 10-Q and therefore do not include all information and footnotes necessary for a fair presentation of financial position, results of operations, and cash flows in conformity with U.S. generally accepted accounting principles. All adjustments consisting of normally recurring accruals that, in the opinion of management, are necessary for a fair presentation of the financial position and results of operations for the periods covered by the report have been included. The accompanying unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated audited financial statements and related notes appearing in the Company's Annual Report on Form 10-K for the year ended December 31, 2021.

These consolidated financial statements include the accounts of the Company, the Bank, and Encompass. Significant intercompany transactions and accounts are eliminated in consolidation.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates — The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the balance sheet date and the 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 include the determination of the allowance for credit losses, the valuation of deferred tax assets, determination of any impairment of goodwill or other intangibles, the valuation of other real estate (if any), and the fair value of financial instruments. These financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2021. There have been no significant changes to the Company’s significant accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021 other than the adoption of ASC 326 as described in Note 1. Summary of Significant Accounting Policies - Accounting Changes, Reclassifications and Restatements and in Note 2 - Loans and Allowance for Credit Losses.

Accounting Changes, Reclassifications and Restatements [Policy Text Block]

Accounting Changes, Reclassifications and Restatements – Certain items in prior financial statements have been reclassified to conform to the current presentation. In addition, on January 1, 2022, we adopted Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” as subsequently updated for certain clarifications, targeted relief and codification improvements. Accounting Standards Codification (“ASC”) Topic 326 (“ASC 326”) replaces the previous “incurred loss” model for measuring credit losses, which encompassed allowances for current known and inherent losses within the portfolio, with an “expected loss” model, which encompasses allowances for losses expected to be incurred over the life of the portfolio. The new current expected credit loss (“CECL”) model requires the measurement of all expected credit losses for financial assets measured at amortized cost and certain off-balance-sheet credit exposures based on historical experience, current conditions, and reasonable and supportable forecasts. ASC 326 also requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASC 326 includes certain changes to the accounting for available-for-sale securities including the requirement to present credit losses as an allowance rather than as a direct write-down for available-for-sale securities management does not intend to sell or believes that it is more likely than not they will be required to sell.

We adopted ASC 326 using the modified retrospective method for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Upon adoption, we recognized an after-tax cumulative effect increase to retained earnings totaling $1.0 million. Operating results for periods after January 1, 2022 are presented in accordance with ASC 326 while prior period amounts continue to be reported in accordance with previously applicable standards and the accounting policies described in our 2021 Form 10-K.

In connection with the adoption of ASC 326, we revised certain accounting policies and implemented certain accounting policy elections. The revised accounting policies are described below.

Financing Receivable, Allowance for Credit Losses, Policy for Uncollectible Amounts [Policy Text Block]

Allowance For Credit Losses - Loans — The allowance for credit losses on loans is a contra-asset valuation account, calculated in accordance with ASC 326, that is deducted from the amortized cost basis of loans to present management's best estimate of the net amount expected to be collected. Loans are charged-off against the allowance when deemed uncollectible by management. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Adjustments to the allowance are reported in our income statement as a component of credit loss expense. Management has made the accounting policy election to exclude accrued interest receivable on loans from the estimate of credit losses. Further information regarding our policies and methodology used to estimate the allowance for credit losses on loans is presented in Note 2 - Loans and Allowance for Credit Losses.

Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block]

Allowance For Credit Losses - Off-Balance-Sheet Credit Exposures — The allowance for credit losses on off-balance-sheet credit exposures is a liability account, calculated in accordance with ASC 326, representing expected credit losses over the contractual period for which we are exposed to credit risk resulting from a contractual obligation to extend credit. No allowance is recognized if we have the unconditional right to cancel the obligation. The allowance is reported as a component of accrued interest payable and other liabilities in our consolidated balance sheets. Adjustments to the allowance are reported in our income statement as a component of non-interest expense. Further information regarding our policies and methodology used to estimate the allowance for credit losses on off-balance-sheet credit exposures is presented in Note 11 - Commitments and Contingent Liabilities.

Investment, Policy [Policy Text Block]

Securities – Securities are classified as held to maturity and carried at amortized cost when management has the positive intent and ability to hold them until maturity. Securities to be held for indefinite periods of time are classified as available for sale and carried at fair value, with the unrealized holding gains and losses (those for which no allowance for credit losses are recorded) reported as a component of other comprehensive earnings, net of tax. Securities held for resale in anticipation of short-term market movements are classified as trading and are carried at fair value, with changes in unrealized holding gains and losses included in income. Management determines the appropriate classification of securities at the time of purchase. Securities with limited marketability, such as stock in the Federal Reserve Bank and the Federal Home Loan Bank, are carried at cost.

Interest income on securities includes amortization of purchase premiums and discounts. Premiums and discounts on securities are generally amortized using the interest method with a constant effective yield without anticipating prepayments, except for mortgage-backed securities where prepayments are anticipated. Premiums on callable securities are amortized to their earliest call date. A security is placed on non-accrual status if (i) principal or interest has been in default for a period of 90 days or more or (ii) full payment of principal and interest is not expected. Interest accrued but not received for a security placed on non-accrual status is reversed against interest income. Gains and losses on sales are recorded on the trade date and are derived from the amortized cost of the security sold.

Allowance for Credit Losses - Securities Available-for-Sale — For any securities classified as available-for-sale that are in an unrealized loss position at the balance sheet date, the Company assesses whether or not it intends to sell the security, or more likely than not will be required to sell the security, before recovery of its amortized cost basis. If either criteria is met, the security's amortized cost basis is written down to fair value through net income. If neither criteria is met, the Company evaluates whether any portion of the decline in fair value is the result of credit deterioration. Such evaluations consider the extent to which the amortized cost of the security exceeds its fair value, changes in credit ratings and any other known adverse conditions related to the specific security. If the evaluation indicates that a credit loss exists, an allowance for credit losses is recorded for the amount by which the amortized cost basis of the security exceeds the present value of cash flows expected to be collected, limited by the amount by which the amortized cost exceeds fair value. Any impairment not recognized in the allowance for credit losses is recognized in other comprehensive income.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently Issued Accounting Pronouncements

Information about certain recently issued accounting standards updates is presented below. Also refer to Note 1 - Accounting Standards Updates in our 2021 Form 10-K for additional information related to previously issued accounting standards updates.

ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” In March 2020, the FASB issued this ASU and has issued subsequent amendments thereto, which provides temporary optional guidance to ease the potential burden in accounting for reference rate reform. The ASU provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued. It is intended to help stakeholders during the global market-wide reference rate transition period. The guidance is effective for all entities as of March 12, 2020 through December 31, 2022. The Company has implemented a transition plan to identify and modify its loans and other financial instruments with attributes that are either directly or indirectly influenced by LIBOR. The Company has discontinued originating LIBOR-based loans during 2022 and has begun negotiating loans primarily using its preferred replacement index, the Secured Overnight Financing Rate ("SOFR"). For the Company’s currently outstanding LIBOR-based loans, the timing and manner in which each customer's contract transitions to SOFR will vary on a case-by-case basis. The Company expects to complete all transitions by August 2023.

ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. As noted above, effective January 1, 2022 the Company adopted ASU 2016-13, which resulted in a $7.6 million decrease to the allowance for credit losses and a $6.2 million increase to the reserve for unfunded commitments, resulting in a $1.0 million increase in retained earnings (net of taxes). See Note 2 – Loans and Allowance for Credit Losses for additional information.

ASU 2022-01, “Derivatives and Hedging (Topic 815): Fair Value Hedging - Portfolio Layer Method.” ASU 2022-01 was issued to expand the scope of assets eligible for portfolio layer method hedging to include all financial assets. The update also expands the current last-of-layer method that permits only one hedged layer to allow multiple hedged layers of a single closed portfolio. The last-of-layer method is renamed the portfolio layer method, because more than the last layer of a portfolio could be hedged. The guidance is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2022. The adoption of ASU 2022-01 is not expected to have a significant impact on our financial statements.

ASU 2022-02, “Financial Instruments - Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures.” ASU 2022-02 was issued to respond to feedback received from post-implementation review of Topic 326. The amendments eliminate the troubled debt restructuring (TDR) recognition and measurement guidance and now require that an entity evaluate whether the modification represents a new loan or a continuation of an existing loan. The amendments enhance existing disclosures and include new disclosure requirements related to certain modifications of receivables made to borrowers experiencing financial difficulty. To improve consistency for vintage disclosures, the ASU requires that public business entities disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases within the scope of Subtopic 326-20. The guidance is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2022. The adoption of ASU 2022-02 is not expected to have a significant impact on our financial statements.

Other than those previously discussed, there were no other recently issued accounting pronouncements that are expected to materially impact the Company.