<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.23.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>489</ContextCount>
  <ElementCount>333</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>76</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-document-and-entity-information</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Consolidated Balance Sheets (Current Period Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-consolidated-balance-sheets-current-period-unaudited</Role>
      <ShortName>Consolidated Balance Sheets (Current Period Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-consolidated-balance-sheets-current-period-unaudited-parentheticals</Role>
      <ShortName>Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Consolidated Statements of Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-consolidated-statements-of-income-unaudited</Role>
      <ShortName>Consolidated Statements of Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Consolidated Statements of Comprehensive Income (Loss) (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-consolidated-statements-of-comprehensive-income-loss-unaudited</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Loss) (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Consolidated Statements of Stockholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-consolidated-statements-of-stockholders-equity-unaudited</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-consolidated-statements-of-stockholders-equity-unaudited-parentheticals</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Statement - Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-consolidated-statements-of-cash-flows-unaudited</Role>
      <ShortName>Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Disclosure - Note 1 - Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-1-significant-accounting-policies</Role>
      <ShortName>Note 1 - Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Note 2 - Dividends</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-2-dividends</Role>
      <ShortName>Note 2 - Dividends</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Note 3 - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-3-earnings-per-share</Role>
      <ShortName>Note 3 - Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Note 4 - Off-balance Sheet Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-4-offbalance-sheet-arrangements</Role>
      <ShortName>Note 4 - Off-balance Sheet Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Note 5 - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-5-fair-value-measurements</Role>
      <ShortName>Note 5 - Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Note 6 - Debt Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities</Role>
      <ShortName>Note 6 - Debt Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Note 8 - Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-</Role>
      <ShortName>Note 8 - Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Note 9 - Pledged Collateral Related to Securities Sold Under Repurchase Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-9-pledged-collateral-related-to-securities-sold-under-repurchase-agreements-</Role>
      <ShortName>Note 9 - Pledged Collateral Related to Securities Sold Under Repurchase Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Note 10 - Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-10-borrowings</Role>
      <ShortName>Note 10 - Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Note 11 - Derivative Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-11-derivative-financial-instruments-</Role>
      <ShortName>Note 11 - Derivative Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Note 12 - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-12-income-taxes</Role>
      <ShortName>Note 12 - Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>020 - Disclosure - Note 13 - Commitments, Contingencies and Concentrations of Credit Risk</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-13-commitments-contingencies-and-concentrations-of-credit-risk</Role>
      <ShortName>Note 13 - Commitments, Contingencies and Concentrations of Credit Risk</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>021 - Disclosure - Note 14 - Regulatory Matters</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-14-regulatory-matters</Role>
      <ShortName>Note 14 - Regulatory Matters</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>022 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-significant-accounting-policies-policies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-1-significant-accounting-policies</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>023 - Disclosure - Note 1 - Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-1-significant-accounting-policies-tables</Role>
      <ShortName>Note 1 - Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-1-significant-accounting-policies</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>024 - Disclosure - Note 5 - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-5-fair-value-measurements-tables</Role>
      <ShortName>Note 5 - Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-5-fair-value-measurements</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>025 - Disclosure - Note 6 - Debt Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities-tables</Role>
      <ShortName>Note 6 - Debt Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>026 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-tables</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>027 - Disclosure - Note 8 - Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-tables</Role>
      <ShortName>Note 8 - Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>028 - Disclosure - Note 9 - Pledged Collateral Related to Securities Sold Under Repurchase Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-9-pledged-collateral-related-to-securities-sold-under-repurchase-agreements-tables</Role>
      <ShortName>Note 9 - Pledged Collateral Related to Securities Sold Under Repurchase Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-9-pledged-collateral-related-to-securities-sold-under-repurchase-agreements-</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>029 - Disclosure - Note 11 - Derivative Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-11-derivative-financial-instruments-tables</Role>
      <ShortName>Note 11 - Derivative Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-11-derivative-financial-instruments-</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>030 - Disclosure - Note 14 - Regulatory Matters (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-14-regulatory-matters-tables</Role>
      <ShortName>Note 14 - Regulatory Matters (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-14-regulatory-matters</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>031 - Disclosure - Note 1 - Significant Accounting Policies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-1-significant-accounting-policies-details-textual</Role>
      <ShortName>Note 1 - Significant Accounting Policies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-1-significant-accounting-policies-tables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>032 - Disclosure - Note 1 - Significant Accounting Policies - Impact of ASC 326 (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-1-significant-accounting-policies-impact-of-asc-326-details</Role>
      <ShortName>Note 1 - Significant Accounting Policies - Impact of ASC 326 (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>033 - Disclosure - Note 2 - Dividends (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-2-dividends-details-textual</Role>
      <ShortName>Note 2 - Dividends (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-2-dividends</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>034 - Disclosure - Note 3 - Earnings Per Share (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-3-earnings-per-share-details-textual</Role>
      <ShortName>Note 3 - Earnings Per Share (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-3-earnings-per-share</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>035 - Disclosure - Note 5 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-5-fair-value-measurements-assets-measured-at-fair-value-on-a-recurring-basis-details</Role>
      <ShortName>Note 5 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>036 - Disclosure - Note 5 - Fair Value Measurements - Assets Measured at Fair Value on a Nonrecurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-5-fair-value-measurements-assets-measured-at-fair-value-on-a-nonrecurring-basis-details</Role>
      <ShortName>Note 5 - Fair Value Measurements - Assets Measured at Fair Value on a Nonrecurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>037 - Disclosure - Note 5 - Fair Value Measurements - Fair Value Quantitative Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-5-fair-value-measurements-fair-value-quantitative-information-details</Role>
      <ShortName>Note 5 - Fair Value Measurements - Fair Value Quantitative Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>038 - Disclosure - Note 5 - Fair Value Measurements - Estimated Fair Values of Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-5-fair-value-measurements-estimated-fair-values-of-financial-instruments-details</Role>
      <ShortName>Note 5 - Fair Value Measurements - Estimated Fair Values of Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>039 - Disclosure - Note 6 - Debt Securities (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities-details-textual</Role>
      <ShortName>Note 6 - Debt Securities (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities-tables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>040 - Disclosure - Note 6 - Debt Securities - Securities Available-for-sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities-securities-availableforsale-details</Role>
      <ShortName>Note 6 - Debt Securities - Securities Available-for-sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>041 - Disclosure - Note 6 - Debt Securities - Debt Securities Available-for-sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities-debt-securities-availableforsale-details</Role>
      <ShortName>Note 6 - Debt Securities - Debt Securities Available-for-sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>042 - Disclosure - Note 6 - Debt Securities - Proceeds, Gains and Losses From Securities Available-for-sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities-proceeds-gains-and-losses-from-securities-availableforsale-details</Role>
      <ShortName>Note 6 - Debt Securities - Proceeds, Gains and Losses From Securities Available-for-sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>043 - Disclosure - Note 6 - Debt Securities - Securities Available-for-sale Continuous Unrealized Loss Position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-6-debt-securities-securities-availableforsale-continuous-unrealized-loss-position-details</Role>
      <ShortName>Note 6 - Debt Securities - Securities Available-for-sale Continuous Unrealized Loss Position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>044 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-details-textual</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-tables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>045 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Composition of Loans Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-composition-of-loans-receivable-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Composition of Loans Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>046 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Activity in Allowance for Loan Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-activity-in-allowance-for-loan-losses-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Activity in Allowance for Loan Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>047 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Allowance for Loan Losses Impairment Analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-allowance-for-loan-losses-impairment-analysis-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Allowance for Loan Losses Impairment Analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>048 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Loans Receivable Impairment Analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-loans-receivable-impairment-analysis-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Loans Receivable Impairment Analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>049 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Amortized Cost Basis of Collateral Dependent Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-amortized-cost-basis-of-collateral-dependent-loans-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Amortized Cost Basis of Collateral Dependent Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>050 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-impaired-loans-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Impaired Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>051 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-average-recorded-investment-and-interest-income-recognized-on-impaired-loans-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>052 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Modified Financing Receivable With Term Extension (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-modified-financing-receivable-with-term-extension-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Modified Financing Receivable With Term Extension (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>053 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Past Due Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-past-due-loans-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Past Due Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>054 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Amortized Cost Basis of Term Loans by Year of Origination (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-amortized-cost-basis-of-term-loans-by-year-of-origination-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Amortized Cost Basis of Term Loans by Year of Origination (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>055 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Credit Risk Profile by Internally Assigned Grade (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-credit-risk-profile-by-internally-assigned-grade-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Credit Risk Profile by Internally Assigned Grade (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>056 - Disclosure - Note 7 - Loans Receivable and Credit Disclosures - Credit Risk Profile Based on Payment Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-7-loans-receivable-and-credit-disclosures-credit-risk-profile-based-on-payment-activity-details</Role>
      <ShortName>Note 7 - Loans Receivable and Credit Disclosures - Credit Risk Profile Based on Payment Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>057 - Disclosure - Note 8 - Intangible Assets (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-details-textual</Role>
      <ShortName>Note 8 - Intangible Assets (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-tables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>058 - Disclosure - Note 8 - Intangible Assets - Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-intangible-assets-details</Role>
      <ShortName>Note 8 - Intangible Assets - Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>059 - Disclosure - Note 8 - Intangible Assets - Intangible Assets Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-intangible-assets-activity-details</Role>
      <ShortName>Note 8 - Intangible Assets - Intangible Assets Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>060 - Disclosure - Note 8 - Intangible Assets - Estimated Remaining Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-8-intangible-assets-estimated-remaining-amortization-expense-details</Role>
      <ShortName>Note 8 - Intangible Assets - Estimated Remaining Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>061 - Disclosure - Note 9 - Pledged Collateral Related to Securities Sold Under Repurchase Agreements - Pledged Collateral at Estimated Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-9-pledged-collateral-related-to-securities-sold-under-repurchase-agreements-pledged-collateral-at-estimated-fair-value-details</Role>
      <ShortName>Note 9 - Pledged Collateral Related to Securities Sold Under Repurchase Agreements - Pledged Collateral at Estimated Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>062 - Disclosure - Note 10 - Borrowings (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-10-borrowings-details-textual</Role>
      <ShortName>Note 10 - Borrowings (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-10-borrowings</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>063 - Disclosure - Note 11 - Derivative Financial Instruments (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-11-derivative-financial-instruments-details-textual</Role>
      <ShortName>Note 11 - Derivative Financial Instruments (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-11-derivative-financial-instruments-tables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>064 - Disclosure - Note 11 - Derivative Financial Instruments - Fair Value Hedges (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-11-derivative-financial-instruments-fair-value-hedges-details</Role>
      <ShortName>Note 11 - Derivative Financial Instruments - Fair Value Hedges (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>065 - Disclosure - Note 13 - Commitments, Contingencies and Concentrations of Credit Risk (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-13-commitments-contingencies-and-concentrations-of-credit-risk-details-textual</Role>
      <ShortName>Note 13 - Commitments, Contingencies and Concentrations of Credit Risk (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-13-commitments-contingencies-and-concentrations-of-credit-risk</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>066 - Disclosure - Note 14 - Regulatory Matters (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-14-regulatory-matters-details-textual</Role>
      <ShortName>Note 14 - Regulatory Matters (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.amesnational.com/20230630/role/statement-note-14-regulatory-matters-tables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="atlo20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>067 - Disclosure - Note 14 - Regulatory Matters - Actual Capital Amounts and Ratios (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amesnational.com/20230630/role/statement-note-14-regulatory-matters-actual-capital-amounts-and-ratios-details</Role>
      <ShortName>Note 14 - Regulatory Matters - Actual Capital Amounts and Ratios (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 19 fact(s) appearing in ix:hidden were eligible for transformation: atlo:FinancingReceivableModifiedNumberOfContracts, atlo:FinancingReceivableModifiedSubsequentDefaultNumberOfContracts, atlo:NumberOfRestructuredLoansGrantingConcessions, dei:EntityRegistrantName, us-gaap:CommonStockDividendsPerShareDeclared, us-gaap:CommonStockParOrStatedValuePerShare, us-gaap:CommonStockSharesAuthorized, us-gaap:CommonStockSharesIssued, us-gaap:CommonStockSharesOutstanding, us-gaap:DebtInstrumentTerm, us-gaap:FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification, us-gaap:FiniteLivedIntangibleAssetUsefulLife -  atlo20230630_10q.htm 8, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="atlo20230630_10q.htm">atlo20230630_10q.htm</File>
    <File>atlo-20230630.xsd</File>
    <File>atlo-20230630_cal.xml</File>
    <File>atlo-20230630_def.xml</File>
    <File>atlo-20230630_lab.xml</File>
    <File>atlo-20230630_pre.xml</File>
    <File>ex_553088.htm</File>
    <File>ex_553089.htm</File>
    <File>ex_553090.htm</File>
    <File>ex_553091.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="2213">http://fasb.org/us-gaap/2023</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2023</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
