<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.20.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>5133</ContextCount>
  <ElementCount>1197</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>661</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>14</UnitCount>
  <MyReports>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>00090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>00100 - Statement - Consolidated Statement of Financial Position</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/StatementConsolidatedStatementOfFinancialPosition</Role>
      <ShortName>Consolidated Statement of Financial Position</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>00200 - Statement - Consolidated Statement of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/StatementConsolidatedStatementOfIncome</Role>
      <ShortName>Consolidated Statement of Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>00300 - Statement - Consolidated Statement of Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/StatementConsolidatedStatementOfOtherComprehensiveIncome</Role>
      <ShortName>Consolidated Statement of Other Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>00400 - Statement - Consolidated Statement of Changes in Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/StatementConsolidatedStatementOfChangesInEquity</Role>
      <ShortName>Consolidated Statement of Changes in Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>00500 - Statement - Consolidated Statement of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/StatementConsolidatedStatementOfCashFlows</Role>
      <ShortName>Consolidated Statement of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>10101 - Disclosure - REPORTING ENTITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureReportingEntity</Role>
      <ShortName>REPORTING ENTITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>10201 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>10301 - Disclosure - JUDGMENTS AND CRITICAL ACCOUNTING ESTIMATES IN APPLYING ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureJudgmentsAndCriticalAccountingEstimatesInApplyingAccountingPolicies</Role>
      <ShortName>JUDGMENTS AND CRITICAL ACCOUNTING ESTIMATES IN APPLYING ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>10401 - Disclosure - RISK MANAGEMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagement</Role>
      <ShortName>RISK MANAGEMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>10501 - Disclosure - ESTIMATION OF FAIR VALUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValue</Role>
      <ShortName>ESTIMATION OF FAIR VALUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>10601 - Disclosure - CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureClassificationOfFinancialAssetsAndFinancialLiabilities</Role>
      <ShortName>CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>10701 - Disclosure - CASH AND CASH EQUIVALENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCashAndCashEquivalents</Role>
      <ShortName>CASH AND CASH EQUIVALENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>10801 - Disclosure - TRADING ASSETS AND LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilities</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>10901 - Disclosure - INVESTMENT SECURITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecurities</Role>
      <ShortName>INVESTMENT SECURITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>11001 - Disclosure - HEDGE ACCOUNTING</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccounting</Role>
      <ShortName>HEDGE ACCOUNTING</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>11101 - Disclosure - LOANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoans</Role>
      <ShortName>LOANS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>11201 - Disclosure - OTHER ACCOUNTS RECEIVABLE, NET</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNet</Role>
      <ShortName>OTHER ACCOUNTS RECEIVABLE, NET</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>11301 - Disclosure - NON-CURRENT ASSETS HELD FOR SALE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonCurrentAssetsHeldForSale</Role>
      <ShortName>NON-CURRENT ASSETS HELD FOR SALE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>11401 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVentures</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>11501 - Disclosure - TANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssets</Role>
      <ShortName>TANGIBLE ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>11601 - Disclosure - CONCESSION ARRANGEMENTS RIGHTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRights</Role>
      <ShortName>CONCESSION ARRANGEMENTS RIGHTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>11701 - Disclosure - GOODWILL</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwill</Role>
      <ShortName>GOODWILL</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>11801 - Disclosure - OTHER INTANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIntangibleAssets</Role>
      <ShortName>OTHER INTANGIBLE ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>11901 - Disclosure - INCOME TAX</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTax</Role>
      <ShortName>INCOME TAX</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>12001 - Disclosure - CUSTOMER DEPOSITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCustomerDeposits</Role>
      <ShortName>CUSTOMER DEPOSITS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>12101 - Disclosure - FINANCIAL OBLIGATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureFinancialObligations</Role>
      <ShortName>FINANCIAL OBLIGATIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>12201 - Disclosure - EMPLOYEE BENEFITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefits</Role>
      <ShortName>EMPLOYEE BENEFITS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>12301 - Disclosure - LEGAL AND OTHER PROVISIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLegalAndOtherProvisions</Role>
      <ShortName>LEGAL AND OTHER PROVISIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>12401 - Disclosure - OTHER LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherLiabilities</Role>
      <ShortName>OTHER LIABILITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>12501 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParent</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>12601 - Disclosure - NON-CONTROLLING INTEREST</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonControllingInterest</Role>
      <ShortName>NON-CONTROLLING INTEREST</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>12701 - Disclosure - COMMITMENTS AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>12801 - Disclosure - INCOME FROM CONTRACTS WITH CUSTOMERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeFromContractsWithCustomers</Role>
      <ShortName>INCOME FROM CONTRACTS WITH CUSTOMERS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>12901 - Disclosure - NET TRADING INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNetTradingIncome</Role>
      <ShortName>NET TRADING INCOME</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>13001 - Disclosure - OTHER INCOME AND EXPENSE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpense</Role>
      <ShortName>OTHER INCOME AND EXPENSE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>13101 - Disclosure - ANALYSIS OF OPERATING SEGMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegments</Role>
      <ShortName>ANALYSIS OF OPERATING SEGMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>13201 - Disclosure - UNCONSOLIDATED STRUCTURED ENTITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureUnconsolidatedStructuredEntities</Role>
      <ShortName>UNCONSOLIDATED STRUCTURED ENTITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>13301 - Disclosure - TRANSFERS OF FINANCIAL ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTransfersOfFinancialAssets</Role>
      <ShortName>TRANSFERS OF FINANCIAL ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>13401 - Disclosure - RELATED PARTIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRelatedParties</Role>
      <ShortName>RELATED PARTIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>13501 - Disclosure - SUBSEQUENT EVENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureSubsequentEvents</Role>
      <ShortName>SUBSEQUENT EVENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>13601 - Disclosure - PARENT COMPANY INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformation</Role>
      <ShortName>PARENT COMPANY INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>20202 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>30103 - Disclosure - REPORTING ENTITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureReportingEntityTables</Role>
      <ShortName>REPORTING ENTITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureReportingEntity</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>30203 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>30403 - Disclosure - RISK MANAGEMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementTables</Role>
      <ShortName>RISK MANAGEMENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureRiskManagement</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>30503 - Disclosure - ESTIMATION OF FAIR VALUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueTables</Role>
      <ShortName>ESTIMATION OF FAIR VALUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureEstimationOfFairValue</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>30603 - Disclosure - CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureClassificationOfFinancialAssetsAndFinancialLiabilitiesTables</Role>
      <ShortName>CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureClassificationOfFinancialAssetsAndFinancialLiabilities</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>30703 - Disclosure - CASH AND CASH EQUIVALENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCashAndCashEquivalentsTables</Role>
      <ShortName>CASH AND CASH EQUIVALENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureCashAndCashEquivalents</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>30803 - Disclosure - TRADING ASSETS AND LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesTables</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilities</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>30903 - Disclosure - INVESTMENT SECURITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesTables</Role>
      <ShortName>INVESTMENT SECURITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureInvestmentSecurities</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>31003 - Disclosure - HEDGE ACCOUNTING (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingTables</Role>
      <ShortName>HEDGE ACCOUNTING (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureHedgeAccounting</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>31103 - Disclosure - LOANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoansTables</Role>
      <ShortName>LOANS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureLoans</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>31203 - Disclosure - OTHER ACCOUNTS RECEIVABLE, NET (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNetTables</Role>
      <ShortName>OTHER ACCOUNTS RECEIVABLE, NET (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNet</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>31303 - Disclosure - NON-CURRENT ASSETS HELD FOR SALE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonCurrentAssetsHeldForSaleTables</Role>
      <ShortName>NON-CURRENT ASSETS HELD FOR SALE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureNonCurrentAssetsHeldForSale</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>31403 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesTables</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVentures</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>31503 - Disclosure - TANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsTables</Role>
      <ShortName>TANGIBLE ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureTangibleAssets</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>31603 - Disclosure - CONCESSION ARRANGEMENTS RIGHTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRightsTables</Role>
      <ShortName>CONCESSION ARRANGEMENTS RIGHTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRights</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>31703 - Disclosure - GOODWILL (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillTables</Role>
      <ShortName>GOODWILL (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureGoodwill</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>31803 - Disclosure - OTHER INTANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIntangibleAssetsTables</Role>
      <ShortName>OTHER INTANGIBLE ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureOtherIntangibleAssets</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>31903 - Disclosure - INCOME TAX (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxTables</Role>
      <ShortName>INCOME TAX (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureIncomeTax</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>32003 - Disclosure - CUSTOMER DEPOSITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCustomerDepositsTables</Role>
      <ShortName>CUSTOMER DEPOSITS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureCustomerDeposits</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>32103 - Disclosure - FINANCIAL OBLIGATIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureFinancialObligationsTables</Role>
      <ShortName>FINANCIAL OBLIGATIONS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureFinancialObligations</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>32203 - Disclosure - EMPLOYEE BENEFITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsTables</Role>
      <ShortName>EMPLOYEE BENEFITS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureEmployeeBenefits</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>32303 - Disclosure - LEGAL AND OTHER PROVISIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLegalAndOtherProvisionsTables</Role>
      <ShortName>LEGAL AND OTHER PROVISIONS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureLegalAndOtherProvisions</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>32403 - Disclosure - OTHER LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherLiabilitiesTables</Role>
      <ShortName>OTHER LIABILITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureOtherLiabilities</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>32503 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentTables</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParent</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>32603 - Disclosure - NON-CONTROLLING INTEREST (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonControllingInterestTables</Role>
      <ShortName>NON-CONTROLLING INTEREST (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureNonControllingInterest</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>32703 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>32803 - Disclosure - INCOME FROM CONTRACTS WITH CUSTOMERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeFromContractsWithCustomersTables</Role>
      <ShortName>INCOME FROM CONTRACTS WITH CUSTOMERS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureIncomeFromContractsWithCustomers</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>32903 - Disclosure - NET TRADING INCOME (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNetTradingIncomeTables</Role>
      <ShortName>NET TRADING INCOME (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureNetTradingIncome</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>33003 - Disclosure - OTHER INCOME AND EXPENSE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpenseTables</Role>
      <ShortName>OTHER INCOME AND EXPENSE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpense</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>33103 - Disclosure - ANALYSIS OF OPERATING SEGMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegmentsTables</Role>
      <ShortName>ANALYSIS OF OPERATING SEGMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegments</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>33203 - Disclosure - UNCONSOLIDATED STRUCTURED ENTITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureUnconsolidatedStructuredEntitiesTables</Role>
      <ShortName>UNCONSOLIDATED STRUCTURED ENTITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureUnconsolidatedStructuredEntities</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>33403 - Disclosure - RELATED PARTIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRelatedPartiesTables</Role>
      <ShortName>RELATED PARTIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureRelatedParties</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>33503 - Disclosure - SUBSEQUENT EVENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureSubsequentEventsTables</Role>
      <ShortName>SUBSEQUENT EVENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>33603 - Disclosure - PARENT COMPANY INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformationTables</Role>
      <ShortName>PARENT COMPANY INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureParentCompanyInformation</ParentRole>
      <Position>77</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>40101 - Disclosure - REPORTING ENTITY - Tabular disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureReportingEntityTabularDisclosureDetails</Role>
      <ShortName>REPORTING ENTITY - Tabular disclosure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>40102 - Disclosure - REPORTING ENTITY - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureReportingEntityTextualDetails</Role>
      <ShortName>REPORTING ENTITY - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>40201 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesTextualDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>40202 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesChangesInAccountingPoliciesDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>40203 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - IFRS 15 Revenue from contracts with customers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesIfrs15RevenueFromContractsWithCustomersDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - IFRS 15 Revenue from contracts with customers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>40204 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impact of IFRS 9 (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesImpactOfIfrs9Details</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impact of IFRS 9 (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>40205 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impairment of financial assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesImpairmentOfFinancialAssetsDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impairment of financial assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>40206 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impact on OCI from Impairment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesImpactOnOciFromImpairmentDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impact on OCI from Impairment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>40207 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, plant and equipment for own use (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesPropertyPlantAndEquipmentForOwnUseDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, plant and equipment for own use (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>40208 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in Presentation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesChangesInPresentationDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in Presentation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>40209 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Consolidated Statement of Income - (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesConsolidatedStatementOfIncomeDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Consolidated Statement of Income - (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>40210 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Leases - (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesLeasesDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Leases - (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>40211 - Disclosure - BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other standards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesOtherStandardsDetails</Role>
      <ShortName>BASIS OF PREPARATION OF THE CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other standards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureBasisOfPreparationOfConsolidatedFinancialStatementsAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>40401 - Disclosure - RISK MANAGEMENT - Consolidated Credit Risk Exposure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementConsolidatedCreditRiskExposureDetails</Role>
      <ShortName>RISK MANAGEMENT - Consolidated Credit Risk Exposure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>40402 - Disclosure - RISK MANAGEMENT - Loans are recorded at amortized cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLoansAreRecordedAtAmortizedCostDetails</Role>
      <ShortName>RISK MANAGEMENT - Loans are recorded at amortized cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>40403 - Disclosure - RISK MANAGEMENT - Probability of default analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementProbabilityOfDefaultAnalysisDetails</Role>
      <ShortName>RISK MANAGEMENT - Probability of default analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>40404 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Trading investments in debt securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioTradingInvestmentsInDebtSecuritiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Trading investments in debt securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>40405 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Investments in debt securities mandatorily at FVTPL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioInvestmentsInDebtSecuritiesMandatorilyAtFvtplDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Investments in debt securities mandatorily at FVTPL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>40406 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Investments in debt securities at FVOCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioInvestmentsInDebtSecuritiesAtFvociDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Investments in debt securities at FVOCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>40407 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Investments in debt securities at amortized cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioInvestmentsInDebtSecuritiesAtAmortizedCostDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Investments in debt securities at amortized cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>40408 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at FVTPL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioOtherAccountsReceivableAtFvtplDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at FVTPL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>40409 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - General (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioOtherAccountsReceivableAtAmortizedCostGeneralDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - General (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>40410 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - Evaluated using general approach - Other accounts receivable and contract assets for corporate customers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioOtherAccountsReceivableAtAmortizedCostEvaluatedUsingGeneralApproachOtherAccountsReceivableAndContractAssetsForCorporateCustomersDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - Evaluated using general approach - Other accounts receivable and contract assets for corporate customers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>40411 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - Evaluated using general approach - By segment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioOtherAccountsReceivableAtAmortizedCostEvaluatedUsingGeneralApproachBySegmentDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - Evaluated using general approach - By segment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>40412 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - Evaluated using simplified approach (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioOtherAccountsReceivableAtAmortizedCostEvaluatedUsingSimplifiedApproachDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Other accounts receivable at amortized cost - Evaluated using simplified approach (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>40413 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioDerivativeInstrumentsAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>40414 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Trading derivatives - Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioDerivativeInstrumentsTradingDerivativesAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Trading derivatives - Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>104</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>40415 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Trading derivatives - Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioDerivativeInstrumentsTradingDerivativesLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Trading derivatives - Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>105</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>40416 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Hedging derivatives - Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioDerivativeInstrumentsHedgingDerivativesAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Hedging derivatives - Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>106</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>40417 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Hedging derivatives - Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioDerivativeInstrumentsHedgingDerivativesLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Derivative instruments - Hedging derivatives - Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>107</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>40418 - Disclosure - RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Cash and cash equivalents (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditQualityOfFinancialAssetsExcludingLoanPortfolioCashAndCashEquivalentsDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit quality of financial assets (excluding loan portfolio) - Cash and cash equivalents (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>108</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>40419 - Disclosure - RISK MANAGEMENT - Mitigation of credit risk, collateral and other (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementMitigationOfCreditRiskCollateralAndOtherDetails</Role>
      <ShortName>RISK MANAGEMENT - Mitigation of credit risk, collateral and other (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>40420 - Disclosure - RISK MANAGEMENT - Credit portfolio per type of guarantees received (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditPortfolioPerTypeOfGuaranteesReceivedDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit portfolio per type of guarantees received (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>110</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>40421 - Disclosure - RISK MANAGEMENT - Credit risk model scenario tables (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditRiskModelScenarioTablesDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit risk model scenario tables (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>111</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>40422 - Disclosure - RISK MANAGEMENT - Scenario of probability weighting in measuring ECL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementScenarioOfProbabilityWeightingInMeasuringEclDetails</Role>
      <ShortName>RISK MANAGEMENT - Scenario of probability weighting in measuring ECL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>112</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>40423 - Disclosure - RISK MANAGEMENT - Credit risk model - loss allowance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditRiskModelLossAllowanceDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit risk model - loss allowance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>113</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>40424 - Disclosure - RISK MANAGEMENT - Loans individually evaluated for impairment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLoansIndividuallyEvaluatedForImpairmentDetails</Role>
      <ShortName>RISK MANAGEMENT - Loans individually evaluated for impairment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>114</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>40425 - Disclosure - RISK MANAGEMENT - Loss allowance roll forward (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLossAllowanceRollForwardDetails</Role>
      <ShortName>RISK MANAGEMENT - Loss allowance roll forward (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>115</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R116.htm</HtmlFileName>
      <LongName>40426 - Disclosure - RISK MANAGEMENT - Impact of the measurement of ECL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementImpactOfMeasurementOfEclDetails</Role>
      <ShortName>RISK MANAGEMENT - Impact of the measurement of ECL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>116</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>40427 - Disclosure - RISK MANAGEMENT - Loss allowance related with CRDS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLossAllowanceRelatedWithCrdsDetails</Role>
      <ShortName>RISK MANAGEMENT - Loss allowance related with CRDS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>117</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R118.htm</HtmlFileName>
      <LongName>40428 - Disclosure - RISK MANAGEMENT - Litigation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLitigationDetails</Role>
      <ShortName>RISK MANAGEMENT - Litigation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>118</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R119.htm</HtmlFileName>
      <LongName>40429 - Disclosure - RISK MANAGEMENT - Changes in gross carrying amount (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementChangesInGrossCarryingAmountDetails</Role>
      <ShortName>RISK MANAGEMENT - Changes in gross carrying amount (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>119</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R120.htm</HtmlFileName>
      <LongName>40430 - Disclosure - RISK MANAGEMENT - Credit Portfolio Assessed Collectively and Individually (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementCreditPortfolioAssessedCollectivelyAndIndividuallyDetails</Role>
      <ShortName>RISK MANAGEMENT - Credit Portfolio Assessed Collectively and Individually (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>120</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R121.htm</HtmlFileName>
      <LongName>40431 - Disclosure - RISK MANAGEMENT - Concentrations of credit risk - Concentration by sector (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementConcentrationsOfCreditRiskConcentrationBySectorDetails</Role>
      <ShortName>RISK MANAGEMENT - Concentrations of credit risk - Concentration by sector (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>121</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R122.htm</HtmlFileName>
      <LongName>40432 - Disclosure - RISK MANAGEMENT - Concentrations of credit risk - Concentration by location (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementConcentrationsOfCreditRiskConcentrationByLocationDetails</Role>
      <ShortName>RISK MANAGEMENT - Concentrations of credit risk - Concentration by location (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>122</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R123.htm</HtmlFileName>
      <LongName>40433 - Disclosure - RISK MANAGEMENT - Concentrations of credit risk - Concentration by currency (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementConcentrationsOfCreditRiskConcentrationByCurrencyDetails</Role>
      <ShortName>RISK MANAGEMENT - Concentrations of credit risk - Concentration by currency (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>123</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R124.htm</HtmlFileName>
      <LongName>40434 - Disclosure - RISK MANAGEMENT - Participation for loan portfolio in foreign currency (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementParticipationForLoanPortfolioInForeignCurrencyDetails</Role>
      <ShortName>RISK MANAGEMENT - Participation for loan portfolio in foreign currency (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>124</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R125.htm</HtmlFileName>
      <LongName>40435 - Disclosure - RISK MANAGEMENT - Investment debt securities - Concentration by sector (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementInvestmentDebtSecuritiesConcentrationBySectorDetails</Role>
      <ShortName>RISK MANAGEMENT - Investment debt securities - Concentration by sector (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>125</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R126.htm</HtmlFileName>
      <LongName>40436 - Disclosure - RISK MANAGEMENT - Investment debt securities - Concentration by location (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementInvestmentDebtSecuritiesConcentrationByLocationDetails</Role>
      <ShortName>RISK MANAGEMENT - Investment debt securities - Concentration by location (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>126</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R127.htm</HtmlFileName>
      <LongName>40437 - Disclosure - RISK MANAGEMENT - Investment debt securities - Concentration by sovereign risk (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementInvestmentDebtSecuritiesConcentrationBySovereignRiskDetails</Role>
      <ShortName>RISK MANAGEMENT - Investment debt securities - Concentration by sovereign risk (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>127</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R128.htm</HtmlFileName>
      <LongName>40438 - Disclosure - RISK MANAGEMENT - Modified Financial Assets - Restructured loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementModifiedFinancialAssetsRestructuredLoansDetails</Role>
      <ShortName>RISK MANAGEMENT - Modified Financial Assets - Restructured loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>128</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R129.htm</HtmlFileName>
      <LongName>40439 - Disclosure - RISK MANAGEMENT - Modified Financial Assets - Foreclosed assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementModifiedFinancialAssetsForeclosedAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Modified Financial Assets - Foreclosed assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>129</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R130.htm</HtmlFileName>
      <LongName>40440 - Disclosure - RISK MANAGEMENT - Modified Financial Assets - Credit commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementModifiedFinancialAssetsCreditCommitmentsDetails</Role>
      <ShortName>RISK MANAGEMENT - Modified Financial Assets - Credit commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>130</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R131.htm</HtmlFileName>
      <LongName>40441 - Disclosure - RISK MANAGEMENT - Offset of financial assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementOffsetOfFinancialAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Offset of financial assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>131</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R132.htm</HtmlFileName>
      <LongName>40442 - Disclosure - RISK MANAGEMENT - Offset of financial liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementOffsetOfFinancialLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Offset of financial liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>132</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R133.htm</HtmlFileName>
      <LongName>40443 - Disclosure - RISK MANAGEMENT - Trading book risk - Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementTradingBookRiskAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Trading book risk - Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>133</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R134.htm</HtmlFileName>
      <LongName>40444 - Disclosure - RISK MANAGEMENT - Trading book risk - Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementTradingBookRiskLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Trading book risk - Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>134</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R135.htm</HtmlFileName>
      <LongName>40445 - Disclosure - RISK MANAGEMENT - Trading book risk - Net position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementTradingBookRiskNetPositionDetails</Role>
      <ShortName>RISK MANAGEMENT - Trading book risk - Net position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>135</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R136.htm</HtmlFileName>
      <LongName>40446 - Disclosure - RISK MANAGEMENT - Risk Management - Regulatory (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementRiskManagementRegulatoryDetails</Role>
      <ShortName>RISK MANAGEMENT - Risk Management - Regulatory (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>136</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R137.htm</HtmlFileName>
      <LongName>40447 - Disclosure - RISK MANAGEMENT - Risk Management - Value at risk (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementRiskManagementValueAtRiskDetails</Role>
      <ShortName>RISK MANAGEMENT - Risk Management - Value at risk (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>137</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R138.htm</HtmlFileName>
      <LongName>40448 - Disclosure - RISK MANAGEMENT - Investment Price Risk in Equity Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementInvestmentPriceRiskInEquityInstrumentsDetails</Role>
      <ShortName>RISK MANAGEMENT - Investment Price Risk in Equity Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>138</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R139.htm</HtmlFileName>
      <LongName>40449 - Disclosure - RISK MANAGEMENT - Structural foreign exchange risk - Sensitivity analysis of foreign exchange effect (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralForeignExchangeRiskSensitivityAnalysisOfForeignExchangeEffectDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural foreign exchange risk - Sensitivity analysis of foreign exchange effect (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>139</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R140.htm</HtmlFileName>
      <LongName>40450 - Disclosure - RISK MANAGEMENT - Structural foreign exchange risk - Financial assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralForeignExchangeRiskFinancialAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural foreign exchange risk - Financial assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>140</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R141.htm</HtmlFileName>
      <LongName>40451 - Disclosure - RISK MANAGEMENT - Structural foreign exchange risk - Financial liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralForeignExchangeRiskFinancialLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural foreign exchange risk - Financial liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>141</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R142.htm</HtmlFileName>
      <LongName>40452 - Disclosure - RISK MANAGEMENT - Structural foreign exchange risk - Net financial asset (liability) position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralForeignExchangeRiskNetFinancialAssetLiabilityPositionDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural foreign exchange risk - Net financial asset (liability) position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>142</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R143.htm</HtmlFileName>
      <LongName>40453 - Disclosure - RISK MANAGEMENT - Structural interest rate risk - Financial assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralInterestRateRiskFinancialAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural interest rate risk - Financial assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>143</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R144.htm</HtmlFileName>
      <LongName>40454 - Disclosure - RISK MANAGEMENT - Structural interest rate risk - Financial liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralInterestRateRiskFinancialLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural interest rate risk - Financial liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>144</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R145.htm</HtmlFileName>
      <LongName>40455 - Disclosure - RISK MANAGEMENT - Structural interest rate risk - Gap analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralInterestRateRiskGapAnalysisDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural interest rate risk - Gap analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>145</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R146.htm</HtmlFileName>
      <LongName>40456 - Disclosure - RISK MANAGEMENT - Structural interest rate risk - Interest bearing assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralInterestRateRiskInterestBearingAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural interest rate risk - Interest bearing assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>146</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R147.htm</HtmlFileName>
      <LongName>40457 - Disclosure - RISK MANAGEMENT - Structural interest rate risk - Interest bearing liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementStructuralInterestRateRiskInterestBearingLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Structural interest rate risk - Interest bearing liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>147</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R148.htm</HtmlFileName>
      <LongName>40458 - Disclosure - RISK MANAGEMENT - Liquidity Risk - Percentages in each country (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLiquidityRiskPercentagesInEachCountryDetails</Role>
      <ShortName>RISK MANAGEMENT - Liquidity Risk - Percentages in each country (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>148</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R149.htm</HtmlFileName>
      <LongName>40459 - Disclosure - RISK MANAGEMENT - Liquidity Risk - Liquid assets and LRI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLiquidityRiskLiquidAssetsAndLriDetails</Role>
      <ShortName>RISK MANAGEMENT - Liquidity Risk - Liquid assets and LRI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>149</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R150.htm</HtmlFileName>
      <LongName>40460 - Disclosure - RISK MANAGEMENT - Liquidity Risk - Undiscounted cash flows of financial assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLiquidityRiskUndiscountedCashFlowsOfFinancialAssetsDetails</Role>
      <ShortName>RISK MANAGEMENT - Liquidity Risk - Undiscounted cash flows of financial assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>150</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R151.htm</HtmlFileName>
      <LongName>40461 - Disclosure - RISK MANAGEMENT - Liquidity Risk - Undiscounted cash flows of financial liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLiquidityRiskUndiscountedCashFlowsOfFinancialLiabilitiesDetails</Role>
      <ShortName>RISK MANAGEMENT - Liquidity Risk - Undiscounted cash flows of financial liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>151</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R152.htm</HtmlFileName>
      <LongName>40462 - Disclosure - RISK MANAGEMENT - Liquidity Risk - Undiscounted cash flows of commitment loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementLiquidityRiskUndiscountedCashFlowsOfCommitmentLoansDetails</Role>
      <ShortName>RISK MANAGEMENT - Liquidity Risk - Undiscounted cash flows of commitment loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>152</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R153.htm</HtmlFileName>
      <LongName>40463 - Disclosure - RISK MANAGEMENT - Regulatory capital management (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementRegulatoryCapitalManagementDetails</Role>
      <ShortName>RISK MANAGEMENT - Regulatory capital management (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>153</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R154.htm</HtmlFileName>
      <LongName>40464 - Disclosure - RISK MANAGEMENT - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRiskManagementTextualDetails</Role>
      <ShortName>RISK MANAGEMENT - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>154</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R155.htm</HtmlFileName>
      <LongName>40501 - Disclosure - ESTIMATION OF FAIR VALUE - Measurements of fair value of assets on a recurring basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueMeasurementsOfFairValueOfAssetsOnRecurringBasisDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Measurements of fair value of assets on a recurring basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>155</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R156.htm</HtmlFileName>
      <LongName>40502 - Disclosure - ESTIMATION OF FAIR VALUE - Measurements of fair value of liabilities on a recurring basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueMeasurementsOfFairValueOfLiabilitiesOnRecurringBasisDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Measurements of fair value of liabilities on a recurring basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>156</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R157.htm</HtmlFileName>
      <LongName>40503 - Disclosure - ESTIMATION OF FAIR VALUE - Measurements at fair value on a non-recurring basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueMeasurementsAtFairValueOnNonRecurringBasisDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Measurements at fair value on a non-recurring basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>157</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R158.htm</HtmlFileName>
      <LongName>40505 - Disclosure - ESTIMATION OF FAIR VALUE - Valuation of equity instruments Level 3 (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueValuationOfEquityInstrumentsLevel3Details</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Valuation of equity instruments Level 3 (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>158</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R159.htm</HtmlFileName>
      <LongName>40506 - Disclosure - ESTIMATION OF FAIR VALUE - Sensitivity analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueSensitivityAnalysisDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Sensitivity analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>159</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R160.htm</HtmlFileName>
      <LongName>40507 - Disclosure - ESTIMATION OF FAIR VALUE - Yield per hectare of rubber crops (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueYieldPerHectareOfRubberCropsDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Yield per hectare of rubber crops (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>160</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R161.htm</HtmlFileName>
      <LongName>40508 - Disclosure - ESTIMATION OF FAIR VALUE - Yield per hectare of palm crops (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueYieldPerHectareOfPalmCropsDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Yield per hectare of palm crops (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>161</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R162.htm</HtmlFileName>
      <LongName>40509 - Disclosure - ESTIMATION OF FAIR VALUE - Extraction rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueExtractionRateDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Extraction rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>162</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R163.htm</HtmlFileName>
      <LongName>40510 - Disclosure - ESTIMATION OF FAIR VALUE - Sensitivity analysis of Biological Assets at fair value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueSensitivityAnalysisOfBiologicalAssetsAtFairValueDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Sensitivity analysis of Biological Assets at fair value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>163</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R164.htm</HtmlFileName>
      <LongName>40511 - Disclosure - ESTIMATION OF FAIR VALUE - Transfers between level 1 and level 2 of the fair value hierarchy (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueTransfersBetweenLevel1AndLevel2OfFairValueHierarchyDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Transfers between level 1 and level 2 of the fair value hierarchy (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>164</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R165.htm</HtmlFileName>
      <LongName>40512 - Disclosure - ESTIMATION OF FAIR VALUE - Fair value of financial assets recognized at amortized cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueFairValueOfFinancialAssetsRecognizedAtAmortizedCostDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Fair value of financial assets recognized at amortized cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>165</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R166.htm</HtmlFileName>
      <LongName>40513 - Disclosure - ESTIMATION OF FAIR VALUE - Fair value of financial liabilities recognized at amortized cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueFairValueOfFinancialLiabilitiesRecognizedAtAmortizedCostDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Fair value of financial liabilities recognized at amortized cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>166</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R167.htm</HtmlFileName>
      <LongName>40514 - Disclosure - ESTIMATION OF FAIR VALUE - Reconciliation Level 3 of the fair value hierarchy (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueReconciliationLevel3OfFairValueHierarchyDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Reconciliation Level 3 of the fair value hierarchy (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>167</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R168.htm</HtmlFileName>
      <LongName>40515 - Disclosure - ESTIMATION OF FAIR VALUE - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEstimationOfFairValueTextualDetails</Role>
      <ShortName>ESTIMATION OF FAIR VALUE - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>168</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R169.htm</HtmlFileName>
      <LongName>40601 - Disclosure - CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES - Financial assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureClassificationOfFinancialAssetsAndFinancialLiabilitiesFinancialAssetsDetails</Role>
      <ShortName>CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES - Financial assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>169</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R170.htm</HtmlFileName>
      <LongName>40602 - Disclosure - CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES - Financial liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureClassificationOfFinancialAssetsAndFinancialLiabilitiesFinancialLiabilitiesDetails</Role>
      <ShortName>CLASSIFICATION OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES - Financial liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>170</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R171.htm</HtmlFileName>
      <LongName>40701 - Disclosure - CASH AND CASH EQUIVALENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCashAndCashEquivalentsDetails</Role>
      <ShortName>CASH AND CASH EQUIVALENTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureCashAndCashEquivalentsTables</ParentRole>
      <Position>171</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R172.htm</HtmlFileName>
      <LongName>40702 - Disclosure - CASH AND CASH EQUIVALENTS - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCashAndCashEquivalentsTextualDetails</Role>
      <ShortName>CASH AND CASH EQUIVALENTS - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>172</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R173.htm</HtmlFileName>
      <LongName>40801 - Disclosure - TRADING ASSETS AND LIABILITIES - Trading assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesTradingAssetsDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Trading assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>173</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R174.htm</HtmlFileName>
      <LongName>40802 - Disclosure - TRADING ASSETS AND LIABILITIES - Trading liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesTradingLiabilitiesDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Trading liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>174</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R175.htm</HtmlFileName>
      <LongName>40803 - Disclosure - TRADING ASSETS AND LIABILITIES - Total trading assets and liabilities, net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesTotalTradingAssetsAndLiabilitiesNetDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Total trading assets and liabilities, net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>175</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R176.htm</HtmlFileName>
      <LongName>40804 - Disclosure - TRADING ASSETS AND LIABILITIES - Investments in debt securities at fair value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesInvestmentsInDebtSecuritiesAtFairValueDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Investments in debt securities at fair value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>176</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R177.htm</HtmlFileName>
      <LongName>40805 - Disclosure - TRADING ASSETS AND LIABILITIES - Investments in equity securities at fair value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesInvestmentsInEquitySecuritiesAtFairValueDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Investments in equity securities at fair value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>177</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R178.htm</HtmlFileName>
      <LongName>40806 - Disclosure - TRADING ASSETS AND LIABILITIES - Trading derivative assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesTradingDerivativeAssetsDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Trading derivative assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>178</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R179.htm</HtmlFileName>
      <LongName>40807 - Disclosure - TRADING ASSETS AND LIABILITIES - Trading derivative liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesTradingDerivativeLiabilitiesDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Trading derivative liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>179</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R180.htm</HtmlFileName>
      <LongName>40808 - Disclosure - TRADING ASSETS AND LIABILITIES - Trading assets in debt securities pledged as collateral (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTradingAssetsAndLiabilitiesTradingAssetsInDebtSecuritiesPledgedAsCollateralDetails</Role>
      <ShortName>TRADING ASSETS AND LIABILITIES - Trading assets in debt securities pledged as collateral (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>180</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R181.htm</HtmlFileName>
      <LongName>40901 - Disclosure - INVESTMENT SECURITIES - Balances of investment securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesBalancesOfInvestmentSecuritiesDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Balances of investment securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>181</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R182.htm</HtmlFileName>
      <LongName>40902 - Disclosure - INVESTMENT SECURITIES - Investments in debt securities mandatorily at FVTPL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesInvestmentsInDebtSecuritiesMandatorilyAtFvtplDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Investments in debt securities mandatorily at FVTPL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>182</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R183.htm</HtmlFileName>
      <LongName>40903 - Disclosure - INVESTMENT SECURITIES - Investments in debt securities at fair value through OCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesInvestmentsInDebtSecuritiesAtFairValueThroughOciDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Investments in debt securities at fair value through OCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>183</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R184.htm</HtmlFileName>
      <LongName>40904 - Disclosure - INVESTMENT SECURITIES - Investments in debt securities at fair value through OCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesInvestmentsInDebtSecuritiesAtFairValueThroughOciDetailss</Role>
      <ShortName>INVESTMENT SECURITIES - Investments in debt securities at fair value through OCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>184</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R185.htm</HtmlFileName>
      <LongName>40905 - Disclosure - INVESTMENT SECURITIES - Investments in debt securities at amortized cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesInvestmentsInDebtSecuritiesAtAmortizedCostDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Investments in debt securities at amortized cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>185</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R186.htm</HtmlFileName>
      <LongName>40906 - Disclosure - INVESTMENT SECURITIES - Investments in equity securities at fair value through OCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesInvestmentsInEquitySecuritiesAtFairValueThroughOciDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Investments in equity securities at fair value through OCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>186</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R187.htm</HtmlFileName>
      <LongName>40907 - Disclosure - INVESTMENT SECURITIES - Equity instruments through OCI - Tabular disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesEquityInstrumentsThroughOciTabularDisclosureDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Equity instruments through OCI - Tabular disclosure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>187</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R188.htm</HtmlFileName>
      <LongName>40908 - Disclosure - INVESTMENT SECURITIES - Equity instruments through OCI - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesEquityInstrumentsThroughOciAdditionalInformationDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Equity instruments through OCI - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>188</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R189.htm</HtmlFileName>
      <LongName>40909 - Disclosure - INVESTMENT SECURITIES - Equity instruments through OCI - Dividend income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesEquityInstrumentsThroughOciDividendIncomeDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Equity instruments through OCI - Dividend income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>189</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R190.htm</HtmlFileName>
      <LongName>40910 - Disclosure - INVESTMENT SECURITIES - Investment assets in debt securities through OCI pledged as collateral (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesInvestmentAssetsInDebtSecuritiesThroughOciPledgedAsCollateralDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Investment assets in debt securities through OCI pledged as collateral (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>190</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R191.htm</HtmlFileName>
      <LongName>40911 - Disclosure - INVESTMENT SECURITIES - Investment assets in debt securities at amortized cost pledged as collateral (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentSecuritiesInvestmentAssetsInDebtSecuritiesAtAmortizedCostPledgedAsCollateralDetails</Role>
      <ShortName>INVESTMENT SECURITIES - Investment assets in debt securities at amortized cost pledged as collateral (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>191</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R192.htm</HtmlFileName>
      <LongName>41001 - Disclosure - HEDGE ACCOUNTING - Changes in the fluctuation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingChangesInFluctuationDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Changes in the fluctuation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>192</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R193.htm</HtmlFileName>
      <LongName>41002 - Disclosure - HEDGE ACCOUNTING - Net Investment in Foreign Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingNetInvestmentInForeignOperationsDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Net Investment in Foreign Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>193</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R194.htm</HtmlFileName>
      <LongName>41003 - Disclosure - HEDGE ACCOUNTING - Hedging operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingHedgingOperationsDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Hedging operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>194</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R195.htm</HtmlFileName>
      <LongName>41004 - Disclosure - HEDGE ACCOUNTING - Cash flow hedges (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingCashFlowHedgesDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Cash flow hedges (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>195</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R196.htm</HtmlFileName>
      <LongName>41005 - Disclosure - HEDGE ACCOUNTING - Accumulated OCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingAccumulatedOciDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Accumulated OCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>196</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R197.htm</HtmlFileName>
      <LongName>41006 - Disclosure - HEDGE ACCOUNTING - Financial instruments for hedging - assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingFinancialInstrumentsForHedgingAssetsDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Financial instruments for hedging - assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>197</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R198.htm</HtmlFileName>
      <LongName>41007 - Disclosure - HEDGE ACCOUNTING - Financial instruments for hedging - liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingFinancialInstrumentsForHedgingLiabilitiesDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Financial instruments for hedging - liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>198</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R199.htm</HtmlFileName>
      <LongName>41008 - Disclosure - HEDGE ACCOUNTING - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureHedgeAccountingTextualDetails</Role>
      <ShortName>HEDGE ACCOUNTING - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>199</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R200.htm</HtmlFileName>
      <LongName>41101 - Disclosure - LOANS - Credit Portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoansCreditPortfolioDetails</Role>
      <ShortName>LOANS - Credit Portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>200</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R201.htm</HtmlFileName>
      <LongName>41102 - Disclosure - LOANS - Loan Portfolio by Maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoansLoanPortfolioByMaturityDetails</Role>
      <ShortName>LOANS - Loan Portfolio by Maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>201</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R202.htm</HtmlFileName>
      <LongName>41103 - Disclosure - LOANS - Interest income by portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoansInterestIncomeByPortfolioDetails</Role>
      <ShortName>LOANS - Interest income by portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>202</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R203.htm</HtmlFileName>
      <LongName>41104 - Disclosure - LOANS - Financial Leasing (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoansFinancialLeasingDetails</Role>
      <ShortName>LOANS - Financial Leasing (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>203</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R204.htm</HtmlFileName>
      <LongName>41105 - Disclosure - LOANS - Financial Leasing Contracts Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoansFinancialLeasingContractsReceivableDetails</Role>
      <ShortName>LOANS - Financial Leasing Contracts Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>204</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R205.htm</HtmlFileName>
      <LongName>41106 - Disclosure - LOANS - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLoansTextualDetails</Role>
      <ShortName>LOANS - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>205</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R206.htm</HtmlFileName>
      <LongName>41201 - Disclosure - OTHER ACCOUNTS RECEIVABLE, NET - Net of Impairment Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNetNetOfImpairmentLossesDetails</Role>
      <ShortName>OTHER ACCOUNTS RECEIVABLE, NET - Net of Impairment Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>206</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R207.htm</HtmlFileName>
      <LongName>41202 - Disclosure - OTHER ACCOUNTS RECEIVABLE, NET - Contract Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNetContractAssetsDetails</Role>
      <ShortName>OTHER ACCOUNTS RECEIVABLE, NET - Contract Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>207</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R208.htm</HtmlFileName>
      <LongName>41203 - Disclosure - OTHER ACCOUNTS RECEIVABLE, NET - Measured at Amortization costs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNetMeasuredAtAmortizationCostsDetails</Role>
      <ShortName>OTHER ACCOUNTS RECEIVABLE, NET - Measured at Amortization costs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>208</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R209.htm</HtmlFileName>
      <LongName>41204 - Disclosure - OTHER ACCOUNTS RECEIVABLE, NET - Others (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNetOthersDetails</Role>
      <ShortName>OTHER ACCOUNTS RECEIVABLE, NET - Others (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>209</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R210.htm</HtmlFileName>
      <LongName>41205 - Disclosure - OTHER ACCOUNTS RECEIVABLE, NET - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherAccountsReceivableNetTextualDetails</Role>
      <ShortName>OTHER ACCOUNTS RECEIVABLE, NET - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>210</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R211.htm</HtmlFileName>
      <LongName>41301 - Disclosure - NON-CURRENT ASSETS HELD FOR SALE - Roll forward (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonCurrentAssetsHeldForSaleRollForwardDetails</Role>
      <ShortName>NON-CURRENT ASSETS HELD FOR SALE - Roll forward (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>211</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R212.htm</HtmlFileName>
      <LongName>41302 - Disclosure - NON-CURRENT ASSETS HELD FOR SALE - Foreclosed Assets, Leasing Agreements, Other (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonCurrentAssetsHeldForSaleForeclosedAssetsLeasingAgreementsOtherDetails</Role>
      <ShortName>NON-CURRENT ASSETS HELD FOR SALE - Foreclosed Assets, Leasing Agreements, Other (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>212</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R213.htm</HtmlFileName>
      <LongName>41303 - Disclosure - NON-CURRENT ASSETS HELD FOR SALE - Associated Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonCurrentAssetsHeldForSaleAssociatedLiabilitiesDetails</Role>
      <ShortName>NON-CURRENT ASSETS HELD FOR SALE - Associated Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>213</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R214.htm</HtmlFileName>
      <LongName>41401 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Tabular disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesTabularDisclosureDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Tabular disclosure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>214</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R215.htm</HtmlFileName>
      <LongName>41402 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Voting Right Percentage (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesVotingRightPercentageDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Voting Right Percentage (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>215</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R216.htm</HtmlFileName>
      <LongName>41403 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Ownership Interest and Book Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesOwnershipInterestAndBookValueDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Ownership Interest and Book Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>216</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R217.htm</HtmlFileName>
      <LongName>41404 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Roll forward of investment in associates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesRollForwardOfInvestmentInAssociatesDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Roll forward of investment in associates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>217</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R218.htm</HtmlFileName>
      <LongName>41405 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Roll forward of investment in joint ventures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesRollForwardOfInvestmentInJointVenturesDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Roll forward of investment in joint ventures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>218</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R219.htm</HtmlFileName>
      <LongName>41406 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Financial information of associates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesFinancialInformationOfAssociatesDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Financial information of associates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>219</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R220.htm</HtmlFileName>
      <LongName>41407 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Financial information of joint ventures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesFinancialInformationOfJointVenturesDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Financial information of joint ventures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>220</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R221.htm</HtmlFileName>
      <LongName>41408 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesTextualDetails</Role>
      <ShortName>INVESTMENTS IN ASSOCIATES AND JOINT VENTURES - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureInvestmentsInAssociatesAndJointVenturesTables</ParentRole>
      <Position>221</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R222.htm</HtmlFileName>
      <LongName>41501 - Disclosure - TANGIBLE ASSETS - Carrying Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsCarryingValueDetails</Role>
      <ShortName>TANGIBLE ASSETS - Carrying Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>222</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R223.htm</HtmlFileName>
      <LongName>41502 - Disclosure - TANGIBLE ASSETS - Properties, plant and equipment balance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsPropertiesPlantAndEquipmentBalanceDetails</Role>
      <ShortName>TANGIBLE ASSETS - Properties, plant and equipment balance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>223</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R224.htm</HtmlFileName>
      <LongName>41503 - Disclosure - TANGIBLE ASSETS - Operating Lease (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsOperatingLeaseDetails</Role>
      <ShortName>TANGIBLE ASSETS - Operating Lease (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>224</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R225.htm</HtmlFileName>
      <LongName>41504 - Disclosure - TANGIBLE ASSETS - Minimum Lease Payments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsMinimumLeasePaymentsDetails</Role>
      <ShortName>TANGIBLE ASSETS - Minimum Lease Payments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>225</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R226.htm</HtmlFileName>
      <LongName>41505 - Disclosure - TANGIBLE ASSETS - Right of Use Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsRightOfUseAssetsDetails</Role>
      <ShortName>TANGIBLE ASSETS - Right of Use Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>226</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R227.htm</HtmlFileName>
      <LongName>41506 - Disclosure - TANGIBLE ASSETS - Biological Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsBiologicalAssetsDetails</Role>
      <ShortName>TANGIBLE ASSETS - Biological Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>227</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R228.htm</HtmlFileName>
      <LongName>41507 - Disclosure - TANGIBLE ASSETS - Area Planted in Hectares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsAreaPlantedInHectaresDetails</Role>
      <ShortName>TANGIBLE ASSETS - Area Planted in Hectares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>228</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R229.htm</HtmlFileName>
      <LongName>41508 - Disclosure - TANGIBLE ASSETS - Hectares Expected Years (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsHectaresExpectedYearsDetails</Role>
      <ShortName>TANGIBLE ASSETS - Hectares Expected Years (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>229</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R230.htm</HtmlFileName>
      <LongName>41509 - Disclosure - TANGIBLE ASSETS - Statement of Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsStatementOfIncomeDetails</Role>
      <ShortName>TANGIBLE ASSETS - Statement of Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>230</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R231.htm</HtmlFileName>
      <LongName>41510 - Disclosure - TANGIBLE ASSETS - Investment properties - Summary (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsInvestmentPropertiesSummaryDetails</Role>
      <ShortName>TANGIBLE ASSETS - Investment properties - Summary (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>231</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R232.htm</HtmlFileName>
      <LongName>41511 - Disclosure - TANGIBLE ASSETS - Investment properties - Amounts recognized in statement of income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsInvestmentPropertiesAmountsRecognizedInStatementOfIncomeDetails</Role>
      <ShortName>TANGIBLE ASSETS - Investment properties - Amounts recognized in statement of income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>232</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R233.htm</HtmlFileName>
      <LongName>41512 - Disclosure - TANGIBLE ASSETS - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTangibleAssetsTextualDetails</Role>
      <ShortName>TANGIBLE ASSETS - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>233</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R234.htm</HtmlFileName>
      <LongName>41601 - Disclosure - CONCESSION ARRANGEMENTS RIGHTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRightsDetails</Role>
      <ShortName>CONCESSION ARRANGEMENTS RIGHTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRightsTables</ParentRole>
      <Position>234</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R235.htm</HtmlFileName>
      <LongName>41602 - Disclosure - CONCESSION ARRANGEMENTS RIGHTS - Financial assets in concession arrangements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRightsFinancialAssetsInConcessionArrangementsDetails</Role>
      <ShortName>CONCESSION ARRANGEMENTS RIGHTS - Financial assets in concession arrangements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>235</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R236.htm</HtmlFileName>
      <LongName>41603 - Disclosure - CONCESSION ARRANGEMENTS RIGHTS - Intangible assets in concession arrangements - Tabular disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRightsIntangibleAssetsInConcessionArrangementsTabularDisclosureDetails</Role>
      <ShortName>CONCESSION ARRANGEMENTS RIGHTS - Intangible assets in concession arrangements - Tabular disclosure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>236</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R237.htm</HtmlFileName>
      <LongName>41604 - Disclosure - CONCESSION ARRANGEMENTS RIGHTS - Intangible assets in concession arrangements - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRightsIntangibleAssetsInConcessionArrangementsAdditionalInformationDetails</Role>
      <ShortName>CONCESSION ARRANGEMENTS RIGHTS - Intangible assets in concession arrangements - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>237</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R238.htm</HtmlFileName>
      <LongName>41605 - Disclosure - CONCESSION ARRANGEMENTS RIGHTS - Summary of the main concession contracts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureConcessionArrangementsRightsSummaryOfMainConcessionContractsDetails</Role>
      <ShortName>CONCESSION ARRANGEMENTS RIGHTS - Summary of the main concession contracts (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>238</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R239.htm</HtmlFileName>
      <LongName>41701 - Disclosure - GOODWILL - Roll forwards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillRollForwardsDetails</Role>
      <ShortName>GOODWILL - Roll forwards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>239</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R240.htm</HtmlFileName>
      <LongName>41702 - Disclosure - GOODWILL - Carrying Amount (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillCarryingAmountDetails</Role>
      <ShortName>GOODWILL - Carrying Amount (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>240</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R241.htm</HtmlFileName>
      <LongName>41703 - Disclosure - GOODWILL - Projection (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillProjectionDetails</Role>
      <ShortName>GOODWILL - Projection (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>241</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R242.htm</HtmlFileName>
      <LongName>41704 - Disclosure - GOODWILL - Cash Generating Units (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillCashGeneratingUnitsDetails</Role>
      <ShortName>GOODWILL - Cash Generating Units (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>242</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R243.htm</HtmlFileName>
      <LongName>41705 - Disclosure - GOODWILL - Cash Generating Units with Allocated Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillCashGeneratingUnitsWithAllocatedGoodwillDetails</Role>
      <ShortName>GOODWILL - Cash Generating Units with Allocated Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>243</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R244.htm</HtmlFileName>
      <LongName>41706 - Disclosure - GOODWILL - Projection Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillProjectionRateDetails</Role>
      <ShortName>GOODWILL - Projection Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>244</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R245.htm</HtmlFileName>
      <LongName>41707 - Disclosure - GOODWILL - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureGoodwillTextualDetails</Role>
      <ShortName>GOODWILL - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>245</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R246.htm</HtmlFileName>
      <LongName>41801 - Disclosure - OTHER INTANGIBLE ASSETS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIntangibleAssetsDetails</Role>
      <ShortName>OTHER INTANGIBLE ASSETS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureOtherIntangibleAssetsTables</ParentRole>
      <Position>246</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R247.htm</HtmlFileName>
      <LongName>41901 - Disclosure - INCOME TAX - Components of the income tax expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxComponentsOfIncomeTaxExpenseDetails</Role>
      <ShortName>INCOME TAX - Components of the income tax expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>247</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R248.htm</HtmlFileName>
      <LongName>41902 - Disclosure - INCOME TAX - Reconciliation between total expenses of income tax and tax expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxReconciliationBetweenTotalExpensesOfIncomeTaxAndTaxExpenseDetails</Role>
      <ShortName>INCOME TAX - Reconciliation between total expenses of income tax and tax expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>248</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R249.htm</HtmlFileName>
      <LongName>41903 - Disclosure - INCOME TAX - Tax losses and excess of presumptive income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxTaxLossesAndExcessOfPresumptiveIncomeDetails</Role>
      <ShortName>INCOME TAX - Tax losses and excess of presumptive income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>249</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R250.htm</HtmlFileName>
      <LongName>41904 - Disclosure - INCOME TAX - Deferred taxes by type of temporary difference (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxDeferredTaxesByTypeOfTemporaryDifferenceDetails</Role>
      <ShortName>INCOME TAX - Deferred taxes by type of temporary difference (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>250</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R251.htm</HtmlFileName>
      <LongName>41905 - Disclosure - INCOME TAX - Deferred tax assets and liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxDeferredTaxAssetsAndLiabilitiesDetails</Role>
      <ShortName>INCOME TAX - Deferred tax assets and liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>251</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R252.htm</HtmlFileName>
      <LongName>41906 - Disclosure - INCOME TAX - Estimates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxEstimatesDetails</Role>
      <ShortName>INCOME TAX - Estimates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>252</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R253.htm</HtmlFileName>
      <LongName>41907 - Disclosure - INCOME TAX - Effect of the current and deferred taxes in each component of other comprehensive income in equity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxEffectOfCurrentAndDeferredTaxesInEachComponentOfOtherComprehensiveIncomeInEquityDetails</Role>
      <ShortName>INCOME TAX - Effect of the current and deferred taxes in each component of other comprehensive income in equity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>253</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R254.htm</HtmlFileName>
      <LongName>41908 - Disclosure - INCOME TAX - Uncertainties in open tax positions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxUncertaintiesInOpenTaxPositionsDetails</Role>
      <ShortName>INCOME TAX - Uncertainties in open tax positions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>254</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R255.htm</HtmlFileName>
      <LongName>41909 - Disclosure - INCOME TAX - Tax uncertainties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxTaxUncertaintiesDetails</Role>
      <ShortName>INCOME TAX - Tax uncertainties (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>255</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R256.htm</HtmlFileName>
      <LongName>41910 - Disclosure - INCOME TAX - Tax returns expiry (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxTaxReturnsExpiryDetails</Role>
      <ShortName>INCOME TAX - Tax returns expiry (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>256</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R257.htm</HtmlFileName>
      <LongName>41911 - Disclosure - INCOME TAX - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeTaxTextualDetails</Role>
      <ShortName>INCOME TAX - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>257</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R258.htm</HtmlFileName>
      <LongName>42001 - Disclosure - CUSTOMER DEPOSITS - Deposits Received (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCustomerDepositsDepositsReceivedDetails</Role>
      <ShortName>CUSTOMER DEPOSITS - Deposits Received (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>258</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R259.htm</HtmlFileName>
      <LongName>42002 - Disclosure - CUSTOMER DEPOSITS - Effective Interest Rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCustomerDepositsEffectiveInterestRatesDetails</Role>
      <ShortName>CUSTOMER DEPOSITS - Effective Interest Rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>259</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R260.htm</HtmlFileName>
      <LongName>42003 - Disclosure - CUSTOMER DEPOSITS - Concentration of Deposits Received (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCustomerDepositsConcentrationOfDepositsReceivedDetails</Role>
      <ShortName>CUSTOMER DEPOSITS - Concentration of Deposits Received (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>260</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R261.htm</HtmlFileName>
      <LongName>42004 - Disclosure - CUSTOMER DEPOSITS - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCustomerDepositsTextualDetails</Role>
      <ShortName>CUSTOMER DEPOSITS - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>261</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R262.htm</HtmlFileName>
      <LongName>42101 - Disclosure - FINANCIAL OBLIGATIONS - Interbank borrowings, overnight funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureFinancialObligationsInterbankBorrowingsOvernightFundsDetails</Role>
      <ShortName>FINANCIAL OBLIGATIONS - Interbank borrowings, overnight funds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>262</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R263.htm</HtmlFileName>
      <LongName>42102 - Disclosure - FINANCIAL OBLIGATIONS - Borrowings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureFinancialObligationsBorrowingsDetails</Role>
      <ShortName>FINANCIAL OBLIGATIONS - Borrowings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>263</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R264.htm</HtmlFileName>
      <LongName>42103 - Disclosure - FINANCIAL OBLIGATIONS - Liabilities maturity date (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureFinancialObligationsLiabilitiesMaturityDateDetails</Role>
      <ShortName>FINANCIAL OBLIGATIONS - Liabilities maturity date (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>264</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R265.htm</HtmlFileName>
      <LongName>42104 - Disclosure - FINANCIAL OBLIGATIONS - Reconciliation of movements of liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureFinancialObligationsReconciliationOfMovementsOfLiabilitiesDetails</Role>
      <ShortName>FINANCIAL OBLIGATIONS - Reconciliation of movements of liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>265</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R266.htm</HtmlFileName>
      <LongName>42105 - Disclosure - FINANCIAL OBLIGATIONS - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureFinancialObligationsTextualDetails</Role>
      <ShortName>FINANCIAL OBLIGATIONS - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>266</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R267.htm</HtmlFileName>
      <LongName>42201 - Disclosure - EMPLOYEE BENEFITS - Liabilities for employee benefits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsLiabilitiesForEmployeeBenefitsDetails</Role>
      <ShortName>EMPLOYEE BENEFITS - Liabilities for employee benefits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>267</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R268.htm</HtmlFileName>
      <LongName>42202 - Disclosure - EMPLOYEE BENEFITS - Post-employment benefit expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsPostEmploymentBenefitExpenseDetails</Role>
      <ShortName>EMPLOYEE BENEFITS - Post-employment benefit expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>268</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R269.htm</HtmlFileName>
      <LongName>42203 - Disclosure - EMPLOYEE BENEFITS - Post-employment and long-term benefits movements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsPostEmploymentAndLongTermBenefitsMovementsDetails</Role>
      <ShortName>EMPLOYEE BENEFITS - Post-employment and long-term benefits movements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>269</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R270.htm</HtmlFileName>
      <LongName>42204 - Disclosure - EMPLOYEE BENEFITS - Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsAssumptionsDetails</Role>
      <ShortName>EMPLOYEE BENEFITS - Assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>270</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R271.htm</HtmlFileName>
      <LongName>42205 - Disclosure - EMPLOYEE BENEFITS - Sensitivity analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsSensitivityAnalysisDetails</Role>
      <ShortName>EMPLOYEE BENEFITS - Sensitivity analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>271</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R272.htm</HtmlFileName>
      <LongName>42206 - Disclosure - EMPLOYEE BENEFITS - Future benefit payments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsFutureBenefitPaymentsDetails</Role>
      <ShortName>EMPLOYEE BENEFITS - Future benefit payments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>272</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R273.htm</HtmlFileName>
      <LongName>42207 - Disclosure - EMPLOYEE BENEFITS - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEmployeeBenefitsTextualDetails</Role>
      <ShortName>EMPLOYEE BENEFITS - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>273</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R274.htm</HtmlFileName>
      <LongName>42301 - Disclosure - LEGAL AND OTHER PROVISIONS - Roll-forward of legal provisions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLegalAndOtherProvisionsRollForwardOfLegalProvisionsDetails</Role>
      <ShortName>LEGAL AND OTHER PROVISIONS - Roll-forward of legal provisions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>274</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R275.htm</HtmlFileName>
      <LongName>42302 - Disclosure - LEGAL AND OTHER PROVISIONS - Legal provisions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureLegalAndOtherProvisionsLegalProvisionsDetails</Role>
      <ShortName>LEGAL AND OTHER PROVISIONS - Legal provisions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>275</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R276.htm</HtmlFileName>
      <LongName>42401 - Disclosure - OTHER LIABILITIES - Accounts payable and other liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherLiabilitiesAccountsPayableAndOtherLiabilitiesDetails</Role>
      <ShortName>OTHER LIABILITIES - Accounts payable and other liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>276</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R277.htm</HtmlFileName>
      <LongName>42402 - Disclosure - OTHER LIABILITIES - Other liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherLiabilitiesOtherLiabilitiesDetails</Role>
      <ShortName>OTHER LIABILITIES - Other liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>277</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R278.htm</HtmlFileName>
      <LongName>42501 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Authorized, issued and outstanding (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentAuthorizedIssuedAndOutstandingDetails</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Authorized, issued and outstanding (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>278</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R279.htm</HtmlFileName>
      <LongName>42502 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Appropriated retained earnings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentAppropriatedRetainedEarningsDetails</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Appropriated retained earnings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>279</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R280.htm</HtmlFileName>
      <LongName>42503 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Declared Dividends (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentDeclaredDividendsDetails</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Declared Dividends (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>280</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R281.htm</HtmlFileName>
      <LongName>42504 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Earnings per share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentEarningsPerShareDetails</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Earnings per share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>281</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R282.htm</HtmlFileName>
      <LongName>42505 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Consolidated Other Comprehensive Income (OCI) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentConsolidatedOtherComprehensiveIncomeOciDetails</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Consolidated Other Comprehensive Income (OCI) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>282</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R283.htm</HtmlFileName>
      <LongName>42506 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Consolidated Other Comprehensive Income (OCI) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentConsolidatedOtherComprehensiveIncomeOciDetailss</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Consolidated Other Comprehensive Income (OCI) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>283</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R284.htm</HtmlFileName>
      <LongName>42507 - Disclosure - EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentTextualDetails</Role>
      <ShortName>EQUITY ATTRIBUTABLE TO OWNERS OF THE PARENT - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureEquityAttributableToOwnersOfParentTables</ParentRole>
      <Position>284</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R285.htm</HtmlFileName>
      <LongName>42601 - Disclosure - NON-CONTROLLING INTEREST - Financial information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonControllingInterestFinancialInformationDetails</Role>
      <ShortName>NON-CONTROLLING INTEREST - Financial information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>285</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R286.htm</HtmlFileName>
      <LongName>42602 - Disclosure - NON-CONTROLLING INTEREST - Non-controlling interests (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNonControllingInterestNonControllingInterestsDetails</Role>
      <ShortName>NON-CONTROLLING INTEREST - Non-controlling interests (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>286</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R287.htm</HtmlFileName>
      <LongName>42701 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureCommitmentsAndContingenciesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>287</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R288.htm</HtmlFileName>
      <LongName>42801 - Disclosure - INCOME FROM CONTRACTS WITH CUSTOMERS - Income and Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeFromContractsWithCustomersIncomeAndExpensesDetails</Role>
      <ShortName>INCOME FROM CONTRACTS WITH CUSTOMERS - Income and Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>288</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R289.htm</HtmlFileName>
      <LongName>42802 - Disclosure - INCOME FROM CONTRACTS WITH CUSTOMERS - Income and Cost for Goods and Services (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureIncomeFromContractsWithCustomersIncomeAndCostForGoodsAndServicesDetails</Role>
      <ShortName>INCOME FROM CONTRACTS WITH CUSTOMERS - Income and Cost for Goods and Services (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>289</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R290.htm</HtmlFileName>
      <LongName>42901 - Disclosure - NET TRADING INCOME (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureNetTradingIncomeDetails</Role>
      <ShortName>NET TRADING INCOME (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureNetTradingIncomeTables</ParentRole>
      <Position>290</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R291.htm</HtmlFileName>
      <LongName>43001 - Disclosure - OTHER INCOME AND EXPENSE - Other income - Tabular disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpenseOtherIncomeTabularDisclosureDetails</Role>
      <ShortName>OTHER INCOME AND EXPENSE - Other income - Tabular disclosure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>291</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R292.htm</HtmlFileName>
      <LongName>43002 - Disclosure - OTHER INCOME AND EXPENSE - Other income - Sale of fixed income investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpenseOtherIncomeSaleOfFixedIncomeInvestmentsDetails</Role>
      <ShortName>OTHER INCOME AND EXPENSE - Other income - Sale of fixed income investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>292</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R293.htm</HtmlFileName>
      <LongName>43003 - Disclosure - OTHER INCOME AND EXPENSE - Other income - Recognition of income from sales with subsequent leasing of assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpenseOtherIncomeRecognitionOfIncomeFromSalesWithSubsequentLeasingOfAssetsDetails</Role>
      <ShortName>OTHER INCOME AND EXPENSE - Other income - Recognition of income from sales with subsequent leasing of assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>293</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R294.htm</HtmlFileName>
      <LongName>43004 - Disclosure - OTHER INCOME AND EXPENSE - Other expense - Tabular disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpenseOtherExpenseTabularDisclosureDetails</Role>
      <ShortName>OTHER INCOME AND EXPENSE - Other expense - Tabular disclosure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>294</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R295.htm</HtmlFileName>
      <LongName>43005 - Disclosure - OTHER INCOME AND EXPENSE - Other expense - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureOtherIncomeAndExpenseOtherExpenseAdditionalInformationDetails</Role>
      <ShortName>OTHER INCOME AND EXPENSE - Other expense - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>295</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R296.htm</HtmlFileName>
      <LongName>43101 - Disclosure - ANALYSIS OF OPERATING SEGMENTS - Statement of financial position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegmentsStatementOfFinancialPositionDetails</Role>
      <ShortName>ANALYSIS OF OPERATING SEGMENTS - Statement of financial position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>296</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R297.htm</HtmlFileName>
      <LongName>43102 - Disclosure - ANALYSIS OF OPERATING SEGMENTS - Statement of income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegmentsStatementOfIncomeDetails</Role>
      <ShortName>ANALYSIS OF OPERATING SEGMENTS - Statement of income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>297</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R298.htm</HtmlFileName>
      <LongName>43103 - Disclosure - ANALYSIS OF OPERATING SEGMENTS - Revenue from contracts with customers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegmentsRevenueFromContractsWithCustomersDetails</Role>
      <ShortName>ANALYSIS OF OPERATING SEGMENTS - Revenue from contracts with customers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>298</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R299.htm</HtmlFileName>
      <LongName>43104 - Disclosure - ANALYSIS OF OPERATING SEGMENTS - Income by country (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegmentsIncomeByCountryDetails</Role>
      <ShortName>ANALYSIS OF OPERATING SEGMENTS - Income by country (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>299</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R300.htm</HtmlFileName>
      <LongName>43105 - Disclosure - ANALYSIS OF OPERATING SEGMENTS - Non-current assets by country (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureAnalysisOfOperatingSegmentsNonCurrentAssetsByCountryDetails</Role>
      <ShortName>ANALYSIS OF OPERATING SEGMENTS - Non-current assets by country (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>300</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R301.htm</HtmlFileName>
      <LongName>43201 - Disclosure - UNCONSOLIDATED STRUCTURED ENTITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureUnconsolidatedStructuredEntitiesDetails</Role>
      <ShortName>UNCONSOLIDATED STRUCTURED ENTITIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.grupoaval.com/role/DisclosureUnconsolidatedStructuredEntitiesTables</ParentRole>
      <Position>301</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R302.htm</HtmlFileName>
      <LongName>43301 - Disclosure - TRANSFERS OF FINANCIAL ASSETS - Textual (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureTransfersOfFinancialAssetsTextualDetails</Role>
      <ShortName>TRANSFERS OF FINANCIAL ASSETS - Textual (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>302</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R303.htm</HtmlFileName>
      <LongName>43401 - Disclosure - RELATED PARTIES - General information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRelatedPartiesGeneralInformationDetails</Role>
      <ShortName>RELATED PARTIES - General information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>303</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R304.htm</HtmlFileName>
      <LongName>43402 - Disclosure - RELATED PARTIES - Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRelatedPartiesTransactionsDetails</Role>
      <ShortName>RELATED PARTIES - Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>304</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R305.htm</HtmlFileName>
      <LongName>43404 - Disclosure - RELATED PARTIES - Compensation of key management personnel (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureRelatedPartiesCompensationOfKeyManagementPersonnelDetails</Role>
      <ShortName>RELATED PARTIES - Compensation of key management personnel (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>305</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R306.htm</HtmlFileName>
      <LongName>43501 - Disclosure - SUBSEQUENT EVENTS - Issuance of bonds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureSubsequentEventsIssuanceOfBondsDetails</Role>
      <ShortName>SUBSEQUENT EVENTS - Issuance of bonds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>306</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R307.htm</HtmlFileName>
      <LongName>43502 - Disclosure - SUBSEQUENT EVENTS - Dividends - Declared (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureSubsequentEventsDividendsDeclaredDetails</Role>
      <ShortName>SUBSEQUENT EVENTS - Dividends - Declared (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>307</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R308.htm</HtmlFileName>
      <LongName>43503 - Disclosure - SUBSEQUENT EVENTS - Dividends - Total income available for disposal (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureSubsequentEventsDividendsTotalIncomeAvailableForDisposalDetails</Role>
      <ShortName>SUBSEQUENT EVENTS - Dividends - Total income available for disposal (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>308</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R309.htm</HtmlFileName>
      <LongName>43504 - Disclosure - SUBSEQUENT EVENTS - Dividends - General information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureSubsequentEventsDividendsGeneralInformationDetails</Role>
      <ShortName>SUBSEQUENT EVENTS - Dividends - General information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>309</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R310.htm</HtmlFileName>
      <LongName>43505 - Disclosure - SUBSEQUENT EVENTS - Dividends - Occasional reserve at disposal (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureSubsequentEventsDividendsOccasionalReserveAtDisposalDetails</Role>
      <ShortName>SUBSEQUENT EVENTS - Dividends - Occasional reserve at disposal (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>310</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R311.htm</HtmlFileName>
      <LongName>43601 - Disclosure - PARENT COMPANY INFORMATION - Statement of Financial Position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformationStatementOfFinancialPositionDetails</Role>
      <ShortName>PARENT COMPANY INFORMATION - Statement of Financial Position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>311</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R312.htm</HtmlFileName>
      <LongName>43602 - Disclosure - PARENT COMPANY INFORMATION - Statement of Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformationStatementOfIncomeDetails</Role>
      <ShortName>PARENT COMPANY INFORMATION - Statement of Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>312</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R313.htm</HtmlFileName>
      <LongName>43603 - Disclosure - PARENT COMPANY INFORMATION - Cash flow (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformationCashFlowDetails</Role>
      <ShortName>PARENT COMPANY INFORMATION - Cash flow (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>313</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R314.htm</HtmlFileName>
      <LongName>43604 - Disclosure - PARENT COMPANY INFORMATION - Investment in Subsidiaries and Associates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformationInvestmentInSubsidiariesAndAssociatesDetails</Role>
      <ShortName>PARENT COMPANY INFORMATION - Investment in Subsidiaries and Associates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>314</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R315.htm</HtmlFileName>
      <LongName>43605 - Disclosure - PARENT COMPANY INFORMATION - Outstanding bonds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformationOutstandingBondsDetails</Role>
      <ShortName>PARENT COMPANY INFORMATION - Outstanding bonds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>315</Position>
    </Report>
    <Report instance="aval-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R316.htm</HtmlFileName>
      <LongName>43606 - Disclosure - PARENT COMPANY INFORMATION - Maturities of bonds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.grupoaval.com/role/DisclosureParentCompanyInformationMaturitiesOfBondsDetails</Role>
      <ShortName>PARENT COMPANY INFORMATION - Maturities of bonds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>316</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>aval-20191231.xml</File>
    <File>aval-20191231.xsd</File>
    <File>aval-20191231_cal.xml</File>
    <File>aval-20191231_def.xml</File>
    <File>aval-20191231_lab.xml</File>
    <File>aval-20191231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.ifrs.org/taxonomy/2019-03-27/ifrs-full</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/country/2017-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/currency/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
