Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The consolidated financial statements include the accounts of American National Bankshares Inc. (NASDAQ: AMNB) (the "Company") and its wholly-owned subsidiary, American National Bank and Trust Company (the "Bank"). The Company is a multi-state bank holding company headquartered in Danville, Virginia. The Bank is a community bank organization serving Virginia and North Carolina with 26 banking offices. In addition to traditional retail, commercial and mortgage offerings, the Bank also provides trust and investment services through its Trust and Investment Services Division. The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires management 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 consolidated financial statements 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 relate to the determination of the allowance for loan losses, goodwill and intangible assets, other-than-temporary impairment of securities, accounting for merger and acquisition activity, accounting for acquired loans with specific credit-related deterioration, and the valuation of deferred tax assets and liabilities. In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments (consisting of normal recurring accruals) necessary to present fairly the results of the interim periods. The results of operations for the interim periods are not necessarily indicative of the results that may occur for any other period. These statements should be read in conjunction with the Notes to Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2021. Certain prior period balances have been reclassified to conform to the current period presentation.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Developments In May 2021, the FASB issued ASU 2021-04, “Earnings Per Share (Topic 260), Debt - Modifications and Extinguishments (Subtopic 470-50), Compensation - Stock Compensation (Topic 718), and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity – Classified Written Call Options (a consensus of the FASB Emerging Issues Task Force).” The ASU addresses how an issuer should account for modifications or an exchange of freestanding written call options classified as equity that is not within the scope of another Topic. Early adoption is permitted. ASU 2021-04 was effective for the Bank/Company on January 1, 2022. The adoption did not have a material impact to the consolidated financial statements. Recent Accounting Pronouncements and Other Authoritative Accounting Guidance In June 2016, the FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments." The amendments in this ASU, among other things, require 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. Financial institutions and other organizations will now use forward-looking information to better inform their credit loss estimates. Many of the loss estimation techniques applied today will still be permitted, although the inputs to those techniques will change to reflect the full amount of expected credit losses. In addition, the ASU amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. The FASB has issued multiple updates to ASU 2016-13 as codified in Topic 326, including ASU's 2019-04, 2019-05, 2019-10, 2019-11, 2020-02, and 2020-03. These ASUs have provided for various minor technical corrections and improvements to the codification as well as other transition matters. Smaller reporting companies who file with the U.S. Securities and Exchange Commission ("SEC") and all other entities who do not file with the SEC are required to apply the guidance for fiscal years, and interim periods within those years, beginning after December 15, 2022. At the one-time evaluation date, the Company qualified as a smaller reporting company and elected to defer the adoption of the standard. The Company has begun running parallel models to assess and refine assumptions and methodologies. Management will continue to refine the model to calculate an adjustment to reserves upon adoption. Effective November 25, 2019, the SEC adopted Staff Accounting Bulletin ("SAB") 119. SAB 119 updated portions of SEC interpretative guidance to align with ASC 326, Financial Instruments - Credit Losses. It covers topics including (1) measuring current expected credit losses; (2) development, governance, and documentation of a systematic methodology; (3) documenting the results of a systematic methodology; and (4) validating a systematic methodology. In March 2022, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2022-02, “Financial Instruments-Credit Losses (Topic 326), Troubled Debt Restructurings and Vintage Disclosures.” ASU 2022-02 addresses areas identified by the FASB as part of its post-implementation review of the credit losses standard (ASU 2016-13) that introduced the CECL model. The amendments eliminate the accounting guidance for troubled debt restructurings by creditors that have adopted the CECL model and enhance the disclosure requirements for loan refinancings and restructurings made with borrowers experiencing financial difficulty. In addition, the amendments require a public business entity to disclose current-period gross write-offs for financing receivables and net investment in leases by year of origination in the vintage disclosures. The amendments in this ASU should be applied prospectively, except for the transition method related to the recognition and measurement of TDRs, an entity has the option to apply a modified retrospective transition method, resulting in a cumulative-effect adjustment to retained earnings in the period of adoption. For entities that have adopted ASU 2016-13, ASU 2022-02 is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. For entities that have not yet adopted ASU 2016-13, the effective dates for ASU 2022-02 are the same as the effective dates in ASU 2016-13. Early adoption is permitted if an entity has adopted ASU 2016-13. An entity may elect to early adopt the amendments about TDRs and related disclosure enhancements separately from the amendments related to vintage disclosures. The Company is currently assessing the impact that ASU 2022-02 will have on its consolidated financial statements.

Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2022

Basis of Accounting, Policy [Policy Text Block]

The consolidated financial statements include the accounts of American National Bankshares Inc. (NASDAQ: AMNB) (the "Company") and its wholly-owned subsidiary, American National Bank and Trust Company (the "Bank"). The Company is a multi-state bank holding company headquartered in Danville, Virginia. The Bank is a community bank organization serving Virginia and North Carolina with 26 banking offices. In addition to traditional retail, commercial and mortgage offerings, the Bank also provides trust and investment services through its Trust and Investment Services Division.

The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires management 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 consolidated financial statements 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 relate to the determination of the allowance for loan losses, goodwill and intangible assets, other-than-temporary impairment of securities, accounting for merger and acquisition activity, accounting for acquired loans with specific credit-related deterioration, and the valuation of deferred tax assets and liabilities.

In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments (consisting of normal recurring accruals) necessary to present fairly the results of the interim periods. The results of operations for the interim periods are not necessarily indicative of the results that may occur for any other period. These statements should be read in conjunction with the Notes to Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2021. Certain prior period balances have been reclassified to conform to the current period presentation.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently Adopted Accounting Developments

In May 2021, the FASB issued ASU 2021-04, “Earnings Per Share (Topic 260), Debt - Modifications and Extinguishments (Subtopic 470-50), Compensation - Stock Compensation (Topic 718), and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity – Classified Written Call Options (a consensus of the FASB Emerging Issues Task Force).” The ASU addresses how an issuer should account for modifications or an exchange of freestanding written call options classified as equity that is not within the scope of another Topic. Early adoption is permitted. ASU 2021-04 was effective for the Bank/Company on January 1, 2022. The adoption did not have a material impact to the consolidated financial statements.

Recent Accounting Pronouncements and Other Authoritative Accounting Guidance

In June 2016, the FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments." The amendments in this ASU, among other things, require 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. Financial institutions and other organizations will now use forward-looking information to better inform their credit loss estimates. Many of the loss estimation techniques applied today will still be permitted, although the inputs to those techniques will change to reflect the full amount of expected credit losses. In addition, the ASU amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. The FASB has issued multiple updates to ASU 2016-13 as codified in Topic 326, including ASU's 2019-04, 2019-05, 2019-10, 2019-11, 2020-02, and 2020-03. These ASUs have provided for various minor technical corrections and improvements to the codification as well as other transition matters. Smaller reporting companies who file with the U.S. Securities and Exchange Commission ("SEC") and all other entities who do not file with the SEC are required to apply the guidance for fiscal years, and interim periods within those years, beginning after December 15, 2022. At the one-time evaluation date, the Company qualified as a smaller reporting company and elected to defer the adoption of the standard. The Company has begun running parallel models to assess and refine assumptions and methodologies. Management will continue to refine the model to calculate an adjustment to reserves upon adoption.

Effective November 25, 2019, the SEC adopted Staff Accounting Bulletin ("SAB") 119. SAB 119 updated portions of SEC interpretative guidance to align with ASC 326, Financial Instruments - Credit Losses. It covers topics including (1) measuring current expected credit losses; (2) development, governance, and documentation of a systematic methodology; (3) documenting the results of a systematic methodology; and (4) validating a systematic methodology.

In March 2022, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2022-02, “Financial Instruments-Credit Losses (Topic 326), Troubled Debt Restructurings and Vintage Disclosures.” ASU 2022-02 addresses areas identified by the FASB as part of its post-implementation review of the credit losses standard (ASU 2016-13) that introduced the CECL model. The amendments eliminate the accounting guidance for troubled debt restructurings by creditors that have adopted the CECL model and enhance the disclosure requirements for loan refinancings and restructurings made with borrowers experiencing financial difficulty. In addition, the amendments require a public business entity to disclose current-period gross write-offs for financing receivables and net investment in leases by year of origination in the vintage disclosures. The amendments in this ASU should be applied prospectively, except for the transition method related to the recognition and measurement of TDRs, an entity has the option to apply a modified retrospective transition method, resulting in a cumulative-effect adjustment to retained earnings in the period of adoption. For entities that have adopted ASU 2016-13, ASU 2022-02 is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. For entities that have not yet adopted ASU 2016-13, the effective dates for ASU 2022-02 are the same as the effective dates in ASU 2016-13. Early adoption is permitted if an entity has adopted ASU 2016-13. An entity may elect to early adopt the amendments about TDRs and related disclosure enhancements separately from the amendments related to vintage disclosures. The Company is currently assessing the impact that ASU 2022-02 will have on its consolidated financial statements.