Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2021
Accounting Policies [Abstract]
Consolidation, Policy [Policy Text Block]	The consolidated financial statements for the three and nine months ended September 30, 2021 and 2020 are unaudited. In the opinion of the management of Ames National Corporation (the "Company"), these financial statements reflect all adjustments, consisting of normal recurring adjustments, necessary to present fairly these consolidated financial statements. The results of operations for the interim periods are not necessarily indicative of results which may be expected for an entire year. Certain information and footnote disclosures normally included in complete financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been omitted in accordance with the requirements for interim financial statements. The interim financial statements and notes thereto should be read in conjunction with the year-end audited financial statements contained in the Company's Annual Report on Form 10-K for the year ended December 31, 2020 (the “Annual Report”). The consolidated financial statements include the accounts of the Company and its wholly-owned banking subsidiaries (the “Banks”). All significant intercompany balances and transactions have been eliminated in consolidation.
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	Goodwill: Goodwill represents the excess of cost over the fair value of net assets acquired. Goodwill resulting from acquisitions is not amortized, but is tested for impairment annually or whenever events change and circumstances indicate that it is more likely than not that an impairment loss has occurred. Goodwill is tested for impairment with an estimation of the fair value of a reporting unit. The fair value of a reporting unit is the price that would be received to sell the unit as a whole in an orderly transaction between market participants at the measurement date. As none of the Company’s reporting units are publicly traded, individual reporting unit fair value determinations cannot be directly correlated to the Company’s stock price. Significant judgment is applied when goodwill is assessed for impairment. This judgment includes developing cash flow projections, selecting appropriate discount rates, identifying relevant market comparables, incorporating general economic and market conditions and selecting an appropriate control premium. The Company completed a quantitative assessment of goodwill as of May 31, 2020 which indicated that goodwill was not impaired. Subsequently, the Company determined there were no adverse changes in criteria and key considerations to the previous assessment. Accordingly, the Company concluded there is no impairment of goodwill as of September 30, 2021.
New Accounting Pronouncements, Policy [Policy Text Block]	New and Pending Accounting Pronouncements: In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The ASU requires an organization to measure 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. Organizations will continue to use judgment to determine which loss estimation method is appropriate for their circumstances. Additionally, the ASU amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. In October 2019, the FASB voted to approve amendments to the effective date of ASU No. 2016-13 for smaller reporting companies, as defined by the SEC, and other non-SEC reporting entities. The amendment delays the effective date for our Company until interim and annual periods beginning after December 15, 2022. The Company continues collecting and retaining loan and credit data and evaluating various loss estimation models, along with refining the implementation of the software and its approach for determining the expected credit losses under the new guidance. The impact of ASU No. 2016-13 on the Company’s financial statements are unknown at this time due to economic uncertainty due to the pandemic. The Company will continue to evaluate the extent of the potential impact.

Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2021

Consolidation, Policy [Policy Text Block]

The consolidated financial statements for the three and nine months ended September 30, 2021 and 2020 are unaudited. In the opinion of the management of Ames National Corporation (the "Company"), these financial statements reflect all adjustments, consisting of normal recurring adjustments, necessary to present fairly these consolidated financial statements. The results of operations for the interim periods are not necessarily indicative of results which may be expected for an entire year. Certain information and footnote disclosures normally included in complete financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been omitted in accordance with the requirements for interim financial statements. The interim financial statements and notes thereto should be read in conjunction with the year-end audited financial statements contained in the Company's Annual Report on Form 10-K for the year ended December 31, 2020 (the “Annual Report”). The consolidated financial statements include the accounts of the Company and its wholly-owned banking subsidiaries (the “Banks”). All significant intercompany balances and transactions have been eliminated in consolidation.

Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]

Goodwill: Goodwill represents the excess of cost over the fair value of net assets acquired. Goodwill resulting from acquisitions is not amortized, but is tested for impairment annually or whenever events change and circumstances indicate that it is more likely than not that an impairment loss has occurred. Goodwill is tested for impairment with an estimation of the fair value of a reporting unit.

The fair value of a reporting unit is the price that would be received to sell the unit as a whole in an orderly transaction between market participants at the measurement date. As none of the Company’s reporting units are publicly traded, individual reporting unit fair value determinations cannot be directly correlated to the Company’s stock price. Significant judgment is applied when goodwill is assessed for impairment. This judgment includes developing cash flow projections, selecting appropriate discount rates, identifying relevant market comparables, incorporating general economic and market conditions and selecting an appropriate control premium. The Company completed a quantitative assessment of goodwill as of May 31, 2020 which indicated that goodwill was not impaired. Subsequently, the Company determined there were no adverse changes in criteria and key considerations to the previous assessment. Accordingly, the Company concluded there is no impairment of goodwill as of September 30, 2021.

New Accounting Pronouncements, Policy [Policy Text Block]

New and Pending Accounting Pronouncements: In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The ASU requires an organization to measure 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. Organizations will continue to use judgment to determine which loss estimation method is appropriate for their circumstances. Additionally, the ASU amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. In October 2019, the FASB voted to approve amendments to the effective date of ASU No. 2016-13 for smaller reporting companies, as defined by the SEC, and other non-SEC reporting entities. The amendment delays the effective date for our Company until interim and annual periods beginning after December 15, 2022. The Company continues collecting and retaining loan and credit data and evaluating various loss estimation models, along with refining the implementation of the software and its approach for determining the expected credit losses under the new guidance. The impact of ASU No. 2016-13 on the Company’s financial statements are unknown at this time due to economic uncertainty due to the pandemic. The Company will continue to evaluate the extent of the potential impact.