<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>632</ContextCount>
  <ElementCount>495</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>129</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>995200090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>995200100 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>995200105 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>995200200 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>995200300 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>995200305 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedStatementsOfComprehensiveIncomeLossParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>995200400 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedStatementsOfChangesInStockholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>995200405 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedStatementsOfChangesInStockholdersEquityParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995200500 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995210101 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995210201 - Disclosure - ACQUISITIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureAcquisitions</Role>
      <ShortName>ACQUISITIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995210301 - Disclosure - SECURITIES AND OTHER INVESTMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestments</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995210401 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLosses</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995210501 - Disclosure - GOODWILL AND INTANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureGoodwillAndIntangibleAssets</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995210601 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeases</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995210701 - Disclosure - BORROWINGS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureBorrowings</Role>
      <ShortName>BORROWINGS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995210801 - Disclosure - COMMITMENTS AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995210901 - Disclosure - DERIVATIVES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureDerivatives</Role>
      <ShortName>DERIVATIVES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995211001 - Disclosure - STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureStockholdersEquity</Role>
      <ShortName>STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995211101 - Disclosure - FAIR VALUE MEASUREMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureFairValueMeasurements</Role>
      <ShortName>FAIR VALUE MEASUREMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995211201 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995211301 - Disclosure - EARNINGS PER SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureEarningsPerShare</Role>
      <ShortName>EARNINGS PER SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995211401 - Disclosure - SEGMENT REPORTING AND REVENUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSegmentReportingAndRevenue</Role>
      <ShortName>SEGMENT REPORTING AND REVENUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995215101 - Disclosure - SUBSEQUENT EVENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSubsequentEvents</Role>
      <ShortName>SUBSEQUENT EVENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>99920102 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>99930203 - Disclosure - ACQUISITIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureAcquisitionsTables</Role>
      <ShortName>ACQUISITIONS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureAcquisitions</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>99930303 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestments</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>99930403 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLosses</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>99930503 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsTables</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureGoodwillAndIntangibleAssets</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>99930603 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeasesTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLeases</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>99930703 - Disclosure - BORROWINGS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureBorrowingsTables</Role>
      <ShortName>BORROWINGS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureBorrowings</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>99930803 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>99930903 - Disclosure - DERIVATIVES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureDerivativesTables</Role>
      <ShortName>DERIVATIVES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureDerivatives</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>99931003 - Disclosure - STOCKHOLDERS' EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureStockholdersEquityTables</Role>
      <ShortName>STOCKHOLDERS' EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureStockholdersEquity</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>99931103 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>99931303 - Disclosure - EARNINGS PER SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureEarningsPerShareTables</Role>
      <ShortName>EARNINGS PER SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureEarningsPerShare</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>99931403 - Disclosure - SEGMENT REPORTING AND REVENUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSegmentReportingAndRevenueTables</Role>
      <ShortName>SEGMENT REPORTING AND REVENUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSegmentReportingAndRevenue</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>99940101 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSummaryOfSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>99940201 - Disclosure - ACQUISITIONS (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureAcquisitionsNarrativeDetails</Role>
      <ShortName>ACQUISITIONS (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureAcquisitionsTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>99940202 - Disclosure - ACQUISITIONS (Consideration Transferred) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureAcquisitionsConsiderationTransferredDetails</Role>
      <ShortName>ACQUISITIONS (Consideration Transferred) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureAcquisitionsTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>99940203 - Disclosure - ACQUISITIONS (Pro Forma Amounts) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureAcquisitionsProFormaAmountsDetails</Role>
      <ShortName>ACQUISITIONS (Pro Forma Amounts) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureAcquisitionsTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>99940301 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsNarrativeDetails</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>99940302 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsAmortizedCostGrossUnrealizedGainsAndLossesAndEstimatedFairValuesOfInvestmentSecuritiesDetails</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>99940303 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Schedule of Gross Unrealized Losses and Fair Value of Investments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsScheduleOfGrossUnrealizedLossesAndFairValueOfInvestmentsDetails</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Schedule of Gross Unrealized Losses and Fair Value of Investments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>99940304 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Schedule of Amortized Cost and Estimated Fair Value of Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsScheduleOfAmortizedCostAndEstimatedFairValueOfSecuritiesDetails</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Schedule of Amortized Cost and Estimated Fair Value of Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>99940305 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Amortized Cost of HTM Securities by Security Type and Credit Rating) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsAmortizedCostOfHtmSecuritiesBySecurityTypeAndCreditRatingDetails</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Amortized Cost of HTM Securities by Security Type and Credit Rating) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>99940306 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Schedule of Carrying Value, Gross Unrealized Gains and Losses and Estimated Fair Value of Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsScheduleOfCarryingValueGrossUnrealizedGainsAndLossesAndEstimatedFairValueOfSecuritiesDetails</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Schedule of Carrying Value, Gross Unrealized Gains and Losses and Estimated Fair Value of Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>99940307 - Disclosure - SECURITIES AND OTHER INVESTMENTS (Gross Realized Gains and Losses on the Sale of Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsGrossRealizedGainsAndLossesOnSaleOfSecuritiesDetails</Role>
      <ShortName>SECURITIES AND OTHER INVESTMENTS (Gross Realized Gains and Losses on the Sale of Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSecuritiesAndOtherInvestmentsTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>99940401 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Stated at Face Amount, Net of Unearned Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleOfStatedAtFaceAmountNetOfUnearnedIncomeDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Stated at Face Amount, Net of Unearned Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>99940402 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesNarrativeDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>99940403 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Aging of the Loan Portfolio by Class) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleOfAgingOfLoanPortfolioByClassDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Aging of the Loan Portfolio by Class) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>99940404 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Loans on Nonaccrual Status) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleOfLoansOnNonaccrualStatusDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Loans on Nonaccrual Status) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>99940405 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Troubled Loan Modifications) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTroubledLoanModificationsDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Troubled Loan Modifications) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>99940406 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule for Allowance for Loan Loss Activity, by Portfolio Segment, Balances for Allowance for Credit Losses, and Loans Based on Impairment Methodology) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleForAllowanceForLoanLossActivityByPortfolioSegmentBalancesForAllowanceForCreditLossesAndLoansBasedOnImpairmentMethodologyDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule for Allowance for Loan Loss Activity, by Portfolio Segment, Balances for Allowance for Credit Losses, and Loans Based on Impairment Methodology) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>99940407 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Loans Acquired) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesScheduleOfLoansAcquiredDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Schedule of Loans Acquired) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>99940408 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Loans Receivables Related Risk Rating) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesLoansReceivablesRelatedRiskRatingDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Loans Receivables Related Risk Rating) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>99940409 - Disclosure - LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Loans Receivables Based on Delinquency Status) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesLoansReceivablesBasedOnDelinquencyStatusDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Loans Receivables Based on Delinquency Status) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLoansAndAllowanceForLoanAndLeaseLossesTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>99940501 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsNarrativeDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>99940502 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Schedule of Information Concerning Intangible Assets with Finite Life) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsScheduleOfInformationConcerningIntangibleAssetsWithFiniteLifeDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Schedule of Information Concerning Intangible Assets with Finite Life) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>99940503 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Schedule of Goodwill and Intangible Assets by Operating Segment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsScheduleOfGoodwillAndIntangibleAssetsByOperatingSegmentDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Schedule of Goodwill and Intangible Assets by Operating Segment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>99940504 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Estimated Remaining Amortization Expense of Intangibles) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsEstimatedRemainingAmortizationExpenseOfIntangiblesDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Estimated Remaining Amortization Expense of Intangibles) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureGoodwillAndIntangibleAssetsTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>99940601 - Disclosure - LEASES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeasesNarrativeDetails</Role>
      <ShortName>LEASES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLeasesTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>99940602 - Disclosure - LEASES (Net Investment in Sales-Type and Direct Financing Lease) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeasesNetInvestmentInSalesTypeAndDirectFinancingLeaseDetails</Role>
      <ShortName>LEASES (Net Investment in Sales-Type and Direct Financing Lease) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLeasesTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>99940603 - Disclosure - LEASES (Lessee Lease Portfolio and Other Supplemental Lease Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeasesLesseeLeasePortfolioAndOtherSupplementalLeaseInformationDetails</Role>
      <ShortName>LEASES (Lessee Lease Portfolio and Other Supplemental Lease Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLeasesTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>99940604 - Disclosure - LEASES (Other Lease Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeasesOtherLeaseInformationDetails</Role>
      <ShortName>LEASES (Other Lease Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLeasesTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>99940605 - Disclosure - LEASES (Lease Cost Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeasesLeaseCostInformationDetails</Role>
      <ShortName>LEASES (Lease Cost Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLeasesTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>99940606 - Disclosure - LEASES (Maturities of Lessor and Lessee Arrangements Outstanding) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureLeasesMaturitiesOfLessorAndLesseeArrangementsOutstandingDetails</Role>
      <ShortName>LEASES (Maturities of Lessor and Lessee Arrangements Outstanding) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureLeasesTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>99940701 - Disclosure - BORROWINGS (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureBorrowingsNarrativeDetails</Role>
      <ShortName>BORROWINGS (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureBorrowingsTables</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>99940702 - Disclosure - BORROWINGS (Short-Term Borrowings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureBorrowingsShortTermBorrowingsDetails</Role>
      <ShortName>BORROWINGS (Short-Term Borrowings) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureBorrowingsTables</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>99940703 - Disclosure - BORROWINGS (Schedule of Available Short-Term Debt) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureBorrowingsScheduleOfAvailableShortTermDebtDetails</Role>
      <ShortName>BORROWINGS (Schedule of Available Short-Term Debt) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureBorrowingsTables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>99940704 - Disclosure - BORROWINGS (Long-Term Borrowings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureBorrowingsLongTermBorrowingsDetails</Role>
      <ShortName>BORROWINGS (Long-Term Borrowings) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureBorrowingsTables</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>99940705 - Disclosure - BORROWINGS (Contractual Maturities of Long-Term Debt) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureBorrowingsContractualMaturitiesOfLongTermDebtDetails</Role>
      <ShortName>BORROWINGS (Contractual Maturities of Long-Term Debt) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureBorrowingsTables</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>99940801 - Disclosure - COMMITMENTS AND CONTINGENCIES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureCommitmentsAndContingenciesNarrativeDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>99940802 - Disclosure - COMMITMENTS AND CONTINGENCIES (Balances of Commitments and Contingencies) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureCommitmentsAndContingenciesBalancesOfCommitmentsAndContingenciesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Balances of Commitments and Contingencies) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>99940803 - Disclosure - COMMITMENTS AND CONTINGENCIES (Schedule of Securities Pledged as Collateral) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureCommitmentsAndContingenciesScheduleOfSecuritiesPledgedAsCollateralDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Schedule of Securities Pledged as Collateral) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>77</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>99940901 - Disclosure - DERIVATIVES (Summary of the Derivatives) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureDerivativesSummaryOfDerivativesDetails</Role>
      <ShortName>DERIVATIVES (Summary of the Derivatives) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureDerivativesTables</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>99940902 - Disclosure - DERIVATIVES (Summary of the Carrying Value of the Company's Hedged Assets in Fair Value Hedges) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureDerivativesSummaryOfCarryingValueOfCompanySHedgedAssetsInFairValueHedgesDetails</Role>
      <ShortName>DERIVATIVES (Summary of the Carrying Value of the Company's Hedged Assets in Fair Value Hedges) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureDerivativesTables</ParentRole>
      <Position>79</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>99941001 - Disclosure - STOCKHOLDERS' EQUITY (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureStockholdersEquityNarrativeDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureStockholdersEquityTables</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>99941002 - Disclosure - STOCKHOLDERS' EQUITY (Change in Accumulated Other Comprehensive Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureStockholdersEquityChangeInAccumulatedOtherComprehensiveIncomeDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY (Change in Accumulated Other Comprehensive Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureStockholdersEquityTables</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>99941101 - Disclosure - FAIR VALUE MEASUREMENTS (Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureFairValueMeasurementsScheduleOfFinancialAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureFairValueMeasurementsTables</ParentRole>
      <Position>82</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>99941102 - Disclosure - FAIR VALUE MEASUREMENTS (Schedule of Financial Assets Measured on a Nonrecurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureFairValueMeasurementsScheduleOfFinancialAssetsMeasuredOnNonrecurringBasisDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Schedule of Financial Assets Measured on a Nonrecurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureFairValueMeasurementsTables</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>99941103 - Disclosure - FAIR VALUE MEASUREMENTS (Carrying Values and Estimated Fair Values of the Company's Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureFairValueMeasurementsCarryingValuesAndEstimatedFairValuesOfCompanySFinancialInstrumentsDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Carrying Values and Estimated Fair Values of the Company's Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureFairValueMeasurementsTables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>99941201 - Disclosure - INCOME TAXES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureIncomeTaxesNarrativeDetails</Role>
      <ShortName>INCOME TAXES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>99941205 - Disclosure - INCOME TAXES (Reconciliation Between Expected and Actual Income Tax Expense and Resulting Effective Tax Rate) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureIncomeTaxesReconciliationBetweenExpectedAndActualIncomeTaxExpenseAndResultingEffectiveTaxRateDetails</Role>
      <ShortName>INCOME TAXES (Reconciliation Between Expected and Actual Income Tax Expense and Resulting Effective Tax Rate) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>99941206 - Disclosure - INCOME TAXES (Schedule of Income Taxes Paid) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureIncomeTaxesScheduleOfIncomeTaxesPaidDetails</Role>
      <ShortName>INCOME TAXES (Schedule of Income Taxes Paid) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>99941301 - Disclosure - EARNINGS PER SHARE (Reconciliation of the Denominators of the Basic and Diluted EPS ) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureEarningsPerShareReconciliationOfDenominatorsOfBasicAndDilutedEpsDetails</Role>
      <ShortName>EARNINGS PER SHARE (Reconciliation of the Denominators of the Basic and Diluted EPS ) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureEarningsPerShareTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>99941401 - Disclosure - SEGMENT REPORTING AND REVENUE (Operating Segment Results) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSegmentReportingAndRevenueOperatingSegmentResultsDetails</Role>
      <ShortName>SEGMENT REPORTING AND REVENUE (Operating Segment Results) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSegmentReportingAndRevenueTables</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>99941402 - Disclosure - SEGMENT REPORTING AND REVENUE (Disaggregation of Noninterest Income by Major Source) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSegmentReportingAndRevenueDisaggregationOfNoninterestIncomeByMajorSourceDetails</Role>
      <ShortName>SEGMENT REPORTING AND REVENUE (Disaggregation of Noninterest Income by Major Source) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSegmentReportingAndRevenueTables</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>99941403 - Disclosure - SEGMENT REPORTING AND REVENUE (Disaggregation of Noninterest Income by Reportable Operating Segment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSegmentReportingAndRevenueDisaggregationOfNoninterestIncomeByReportableOperatingSegmentDetails</Role>
      <ShortName>SEGMENT REPORTING AND REVENUE (Disaggregation of Noninterest Income by Reportable Operating Segment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSegmentReportingAndRevenueTables</ParentRole>
      <Position>91</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>99941404 - Disclosure - SEGMENT REPORTING AND REVENUE (Disaggregation of Noninterest Expense by Reportable Operating Segment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSegmentReportingAndRevenueDisaggregationOfNoninterestExpenseByReportableOperatingSegmentDetails</Role>
      <ShortName>SEGMENT REPORTING AND REVENUE (Disaggregation of Noninterest Expense by Reportable Operating Segment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSegmentReportingAndRevenueTables</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="aub-20260331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>99941501 - Disclosure - SUBSEQUENT EVENTS (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://aub.com/role/DisclosureSubsequentEventsNarrativeDetails</Role>
      <ShortName>SUBSEQUENT EVENTS (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://aub.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>93</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>aub-20260331.xsd</File>
    <File>aub-20260331_cal.xml</File>
    <File>aub-20260331_def.xml</File>
    <File>aub-20260331_lab.xml</File>
    <File>aub-20260331_pre.xml</File>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="aub-20260331x10q.htm">aub-20260331x10q.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="2">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="1770">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="32">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
