<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.4</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>995</ContextCount>
  <ElementCount>698</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>246</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>12</UnitCount>
  <MyReports>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DocumentandEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Document - Audit Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AuditInformation</Role>
      <ShortName>Audit Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - Consolidated Statements Of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>Consolidated Statements Of Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedStatementsofComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedStatementsofComprehensiveIncomeParenthetical</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952157 - Statement - Consolidated Statements Of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements Of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Statement - Consolidated Statements Of Changes In Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedStatementsOfChangesInStockholdersEquity</Role>
      <ShortName>Consolidated Statements Of Changes In Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Statement - Consolidated Statements Of Changes In Stockholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityParenthetical</Role>
      <ShortName>Consolidated Statements Of Changes In Stockholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Summary Of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary Of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/OtherComprehensiveIncome</Role>
      <ShortName>Other Comprehensive Income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Revenue Recognition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/RevenueRecognition</Role>
      <ShortName>Revenue Recognition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Acquisitions, Dispositions And Other Adjustments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AcquisitionsDispositionsAndOtherAdjustments</Role>
      <ShortName>Acquisitions, Dispositions And Other Adjustments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Property, Plant And Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PropertyPlantAndEquipment</Role>
      <ShortName>Property, Plant And Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Goodwill And Other Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillAndOtherIntangibleAssets</Role>
      <ShortName>Goodwill And Other Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - Equity Method Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/EquityMethodInvestments</Role>
      <ShortName>Equity Method Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9952171 - Disclosure - Fair Value Measurements And Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosure</Role>
      <ShortName>Fair Value Measurements And Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9952172 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9952173 - Disclosure - Pension And Postretirement Benefits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefits</Role>
      <ShortName>Pension And Postretirement Benefits</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9952174 - Disclosure - Share-Based Payments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ShareBasedPayments</Role>
      <ShortName>Share-Based Payments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9952175 - Disclosure - Stockholders' and Mezzanine Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/StockholdersandMezzanineEquity</Role>
      <ShortName>Stockholders' and Mezzanine Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9952176 - Disclosure - Sales Of Receivables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivables</Role>
      <ShortName>Sales Of Receivables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9952177 - Disclosure - Tower Transaction</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/TowerTransaction</Role>
      <ShortName>Tower Transaction</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9952178 - Disclosure - Transactions With DIRECTV Disclosures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/TransactionsWithDIRECTVDisclosures</Role>
      <ShortName>Transactions With DIRECTV Disclosures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9952179 - Disclosure - FirstNet</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FirstNet</Role>
      <ShortName>FirstNet</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9952180 - Disclosure - Contingent Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ContingentLiabilities</Role>
      <ShortName>Contingent Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9952181 - Disclosure - Supplier and Vendor Financing Programs</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SupplierandVendorFinancingPrograms</Role>
      <ShortName>Supplier and Vendor Financing Programs</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9952182 - Disclosure - Additional Financial Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AdditionalFinancialInformation</Role>
      <ShortName>Additional Financial Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9952183 - Disclosure - Schedule II - Valuation And Qualifying Accounts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ScheduleIIValuationAndQualifyingAccounts</Role>
      <ShortName>Schedule II - Valuation And Qualifying Accounts</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure</Role>
      <ShortName>Cybersecurity Risk Management and Strategy Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - Summary Of Significant Accounting Policies (Policy)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SummaryOfSignificantAccountingPoliciesPolicy</Role>
      <ShortName>Summary Of Significant Accounting Policies (Policy)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://att.com/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/EarningsPerShare</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/OtherComprehensiveIncomeTables</Role>
      <ShortName>Other Comprehensive Income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/OtherComprehensiveIncome</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/SegmentInformation</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - Revenue Recognition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/RevenueRecognitionTables</Role>
      <ShortName>Revenue Recognition (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/RevenueRecognition</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - Property, Plant And Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PropertyPlantAndEquipmentTables</Role>
      <ShortName>Property, Plant And Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/PropertyPlantAndEquipment</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/Leases</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - Goodwill And Other Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillAndOtherIntangibleAssetsTables</Role>
      <ShortName>Goodwill And Other Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/GoodwillAndOtherIntangibleAssets</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - Equity Method Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/EquityMethodInvestmentsTables</Role>
      <ShortName>Equity Method Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/EquityMethodInvestments</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/Debt</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - Fair Value Measurements And Disclosure (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosureTables</Role>
      <ShortName>Fair Value Measurements And Disclosure (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/FairValueMeasurementsAndDisclosure</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxes</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - Pension And Postretirement Benefits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsTables</Role>
      <ShortName>Pension And Postretirement Benefits (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefits</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - Share-Based Payments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ShareBasedPaymentsTables</Role>
      <ShortName>Share-Based Payments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/ShareBasedPayments</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - Sales Of Receivables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivablesTables</Role>
      <ShortName>Sales Of Receivables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/SalesOfReceivables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - Transaction With DIRECTV (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/TransactionWithDIRECTVTables</Role>
      <ShortName>Transaction With DIRECTV (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - Supplier and Vendor Financing Programs (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SupplierandVendorFinancingProgramsTables</Role>
      <ShortName>Supplier and Vendor Financing Programs (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/SupplierandVendorFinancingPrograms</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - Additional Financial Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AdditionalFinancialInformationTables</Role>
      <ShortName>Additional Financial Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://att.com/role/AdditionalFinancialInformation</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - Summary Of Significant Accounting Policies (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SummaryOfSignificantAccountingPoliciesPolicy</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/EarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/EarningsPerShareTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/OtherComprehensiveIncomeDetails</Role>
      <ShortName>Other Comprehensive Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/OtherComprehensiveIncomeTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - Segment Information (Summary Of Operating Revenues And Expenses By Segment) (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SegmentInformationSummaryOfOperatingRevenuesAndExpensesBySegmentNarrativeDetails</Role>
      <ShortName>Segment Information (Summary Of Operating Revenues And Expenses By Segment) (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SegmentInformationTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - Segment Information (Summary Of Operating Revenues And Expenses By Segment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SegmentInformationSummaryOfOperatingRevenuesAndExpensesBySegmentDetails</Role>
      <ShortName>Segment Information (Summary Of Operating Revenues And Expenses By Segment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SegmentInformationTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - Segment Information (Reconciliation Of Operating Income (Loss) to Consolidated Statement Of Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SegmentInformationReconciliationOfOperatingIncomeLosstoConsolidatedStatementOfIncomeDetails</Role>
      <ShortName>Segment Information (Reconciliation Of Operating Income (Loss) to Consolidated Statement Of Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SegmentInformationTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - Segment Information (Schedule of Schedule of Revenues Earned from Customers and Property, Plant and Equipment by Geographical Areas) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SegmentInformationScheduleofScheduleofRevenuesEarnedfromCustomersandPropertyPlantandEquipmentbyGeographicalAreasDetails</Role>
      <ShortName>Segment Information (Schedule of Schedule of Revenues Earned from Customers and Property, Plant and Equipment by Geographical Areas) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SegmentInformationTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - Segment Information (Intersegment Assets, Equity Affiliates Investments and Capital Expenditures Details) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SegmentInformationIntersegmentAssetsEquityAffiliatesInvestmentsandCapitalExpendituresDetailsDetails</Role>
      <ShortName>Segment Information (Intersegment Assets, Equity Affiliates Investments and Capital Expenditures Details) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SegmentInformationTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - Revenue Recognition (Contract with Customer) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/RevenueRecognitionContractwithCustomerDetails</Role>
      <ShortName>Revenue Recognition (Contract with Customer) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/RevenueRecognitionTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - Revenue Recognition (Revenue Categories) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/RevenueRecognitionRevenueCategoriesDetails</Role>
      <ShortName>Revenue Recognition (Revenue Categories) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/RevenueRecognitionTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - Revenue Recognition (Deferred Contract Acquisition and Fulfillment Costs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/RevenueRecognitionDeferredContractAcquisitionandFulfillmentCostsDetails</Role>
      <ShortName>Revenue Recognition (Deferred Contract Acquisition and Fulfillment Costs) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/RevenueRecognitionTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - Revenue Recognition (Contract Assets and Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/RevenueRecognitionContractAssetsandLiabilitiesDetails</Role>
      <ShortName>Revenue Recognition (Contract Assets and Liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/RevenueRecognitionTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - Revenue Recognition (Remaining Performance Obligations) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/RevenueRecognitionRemainingPerformanceObligationsDetails</Role>
      <ShortName>Revenue Recognition (Remaining Performance Obligations) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/RevenueRecognitionTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - Acquisitions, Dispositions And Other Adjustments (Spectrum Auctions Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AcquisitionsDispositionsAndOtherAdjustmentsSpectrumAuctionsNarrativeDetails</Role>
      <ShortName>Acquisitions, Dispositions And Other Adjustments (Spectrum Auctions Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/AcquisitionsDispositionsAndOtherAdjustments</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - Acquisitions, Dispositions And Other Adjustments (Pending Business Acquisition) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AcquisitionsDispositionsAndOtherAdjustmentsPendingBusinessAcquisitionDetails</Role>
      <ShortName>Acquisitions, Dispositions And Other Adjustments (Pending Business Acquisition) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/AcquisitionsDispositionsAndOtherAdjustments</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - Property, Plant And Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PropertyPlantAndEquipmentDetails</Role>
      <ShortName>Property, Plant And Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PropertyPlantAndEquipmentTables</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - Property, Plant And Equipment (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PropertyPlantAndEquipmentNarrativeDetails</Role>
      <ShortName>Property, Plant And Equipment (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PropertyPlantAndEquipmentTables</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - Leases (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/LeasesNarrativeDetails</Role>
      <ShortName>Leases (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/LeasesTables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - Leases (Components of Lease Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/LeasesComponentsofLeaseExpenseDetails</Role>
      <ShortName>Leases (Components of Lease Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/LeasesTables</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - Leases (Supplemental Cash Flow Information Related to Leases) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/LeasesSupplementalCashFlowInformationRelatedtoLeasesDetails</Role>
      <ShortName>Leases (Supplemental Cash Flow Information Related to Leases) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/LeasesTables</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - Leases (Supplemental Balance Sheet Information Related to Leases) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/LeasesSupplementalBalanceSheetInformationRelatedtoLeasesDetails</Role>
      <ShortName>Leases (Supplemental Balance Sheet Information Related to Leases) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/LeasesTables</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - Leases (Future Minimum Maturities of Lease Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/LeasesFutureMinimumMaturitiesofLeaseLiabilitiesDetails</Role>
      <ShortName>Leases (Future Minimum Maturities of Lease Liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/LeasesTables</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - Goodwill And Other Intangible Assets (Summary Of Changes In Carrying Amount Of Goodwill, By Segment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillAndOtherIntangibleAssetsSummaryOfChangesInCarryingAmountOfGoodwillBySegmentDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Summary Of Changes In Carrying Amount Of Goodwill, By Segment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>77</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - Goodwill And Other Intangible Assets (Schedule Of Amortized Intangible Assets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfAmortizedIntangibleAssetsDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Schedule Of Amortized Intangible Assets) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - Goodwill And Other Intangible Assets (Schedule Of Indefinite-Life Intangible Assets Not Subject To Amortization) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfIndefiniteLifeIntangibleAssetsNotSubjectToAmortizationDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Schedule Of Indefinite-Life Intangible Assets Not Subject To Amortization) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>79</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - Goodwill And Other Intangible Assets (Indefinite-Lived Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillAndOtherIntangibleAssetsIndefiniteLivedNarrativeDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Indefinite-Lived Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - Goodwill And Other Intangible Assets (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillAndOtherIntangibleAssetsNarrativeDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - Goodwill and Other Intangible Assets (Schedule of Amortized Intangible Expenses) (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/GoodwillandOtherIntangibleAssetsScheduleofAmortizedIntangibleExpensesNarrativeDetails</Role>
      <ShortName>Goodwill and Other Intangible Assets (Schedule of Amortized Intangible Expenses) (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - Equity Method Investments (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/EquityMethodInvestmentsNarrativeDetails</Role>
      <ShortName>Equity Method Investments (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/EquityMethodInvestmentsTables</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - Equity Method Investments (Reconciliation Of Investments In Equity Affiliates) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/EquityMethodInvestmentsReconciliationOfInvestmentsInEquityAffiliatesDetails</Role>
      <ShortName>Equity Method Investments (Reconciliation Of Investments In Equity Affiliates) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/EquityMethodInvestmentsTables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - Debt (Summary Of Long-Term Debt Of AT&amp;T And Its Subsidiaries) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DebtSummaryOfLongTermDebtOfATTAndItsSubsidiariesDetails</Role>
      <ShortName>Debt (Summary Of Long-Term Debt Of AT&amp;T And Its Subsidiaries) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/DebtTables</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - Debt (Schedule of Debt Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DebtScheduleofDebtActivityDetails</Role>
      <ShortName>Debt (Schedule of Debt Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/DebtTables</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - Debt (Long-Term Debt - Scheduled Repayments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DebtLongTermDebtScheduledRepaymentsDetails</Role>
      <ShortName>Debt (Long-Term Debt - Scheduled Repayments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/DebtTables</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - Debt (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DebtNarrativeDetails</Role>
      <ShortName>Debt (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/DebtTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - Debt (Financing Activities) (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DebtFinancingActivitiesNarrativeDetails</Role>
      <ShortName>Debt (Financing Activities) (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/DebtTables</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>9955564 - Disclosure - Debt (Credit Facilities) (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/DebtCreditFacilitiesNarrativeDetails</Role>
      <ShortName>Debt (Credit Facilities) (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/DebtTables</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>9955565 - Disclosure - Fair Value Measurements And Disclosure (Long-Term Debt And Other Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosureLongTermDebtAndOtherFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Measurements And Disclosure (Long-Term Debt And Other Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/FairValueMeasurementsAndDisclosureTables</ParentRole>
      <Position>91</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>9955566 - Disclosure - Fair Value Measurements And Disclosure (Fair Value Leveling) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosureFairValueLevelingDetails</Role>
      <ShortName>Fair Value Measurements And Disclosure (Fair Value Leveling) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/FairValueMeasurementsAndDisclosureTables</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>9955567 - Disclosure - Fair Value Measurements And Disclosure (Gain and Losses on Equity Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosureGainandLossesonEquitySecuritiesDetails</Role>
      <ShortName>Fair Value Measurements And Disclosure (Gain and Losses on Equity Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/FairValueMeasurementsAndDisclosureTables</ParentRole>
      <Position>93</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>9955568 - Disclosure - Fair Value Measurements And Disclosure (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosureNarrativeDetails</Role>
      <ShortName>Fair Value Measurements And Disclosure (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/FairValueMeasurementsAndDisclosureTables</ParentRole>
      <Position>94</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>9955569 - Disclosure - Fair Value Measurements And Disclosure (Notional Amount Of Our Outstanding Derivative Positions) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosureNotionalAmountOfOurOutstandingDerivativePositionsDetails</Role>
      <ShortName>Fair Value Measurements And Disclosure (Notional Amount Of Our Outstanding Derivative Positions) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/FairValueMeasurementsAndDisclosureTables</ParentRole>
      <Position>95</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>9955570 - Disclosure - Fair Value Measurements And Disclosure (Effect Of Derivatives On The Consolidated Statements Of Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FairValueMeasurementsAndDisclosureEffectOfDerivativesOnTheConsolidatedStatementsOfIncomeDetails</Role>
      <ShortName>Fair Value Measurements And Disclosure (Effect Of Derivatives On The Consolidated Statements Of Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/FairValueMeasurementsAndDisclosureTables</ParentRole>
      <Position>96</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>9955571 - Disclosure - Income Taxes (Components Of Deferred Tax Liabilities (Assets)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesComponentsOfDeferredTaxLiabilitiesAssetsDetails</Role>
      <ShortName>Income Taxes (Components Of Deferred Tax Liabilities (Assets)) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxesTables</ParentRole>
      <Position>97</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>9955572 - Disclosure - Income Taxes (Changes In Unrecognized Tax Benefits Balance For Federal State And Foreign Tax) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesChangesInUnrecognizedTaxBenefitsBalanceForFederalStateAndForeignTaxDetails</Role>
      <ShortName>Income Taxes (Changes In Unrecognized Tax Benefits Balance For Federal State And Foreign Tax) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxesTables</ParentRole>
      <Position>98</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>9955573 - Disclosure - Income Taxes (Components of Income Tax Expense (Benefit)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesComponentsofIncomeTaxExpenseBenefitDetails</Role>
      <ShortName>Income Taxes (Components of Income Tax Expense (Benefit)) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxesTables</ParentRole>
      <Position>99</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>9955574 - Disclosure - Income Taxes (Schedule of Income before Income Tax, Domestic and Foreign) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesScheduleofIncomebeforeIncomeTaxDomesticandForeignDetails</Role>
      <ShortName>Income Taxes (Schedule of Income before Income Tax, Domestic and Foreign) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxesTables</ParentRole>
      <Position>100</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>9955575 - Disclosure - Income Taxes (Reconciliation Of Income Tax Expense (Benefit) Based On Federal Statutory Rate To Amount Per Effective Tax Rate) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesReconciliationOfIncomeTaxExpenseBenefitBasedOnFederalStatutoryRateToAmountPerEffectiveTaxRateDetails</Role>
      <ShortName>Income Taxes (Reconciliation Of Income Tax Expense (Benefit) Based On Federal Statutory Rate To Amount Per Effective Tax Rate) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxesTables</ParentRole>
      <Position>101</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>9955576 - Disclosure - Income Taxes (Cash Income Taxes Paid, Net of Amounts Refunded) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesCashIncomeTaxesPaidNetofAmountsRefundedDetails</Role>
      <ShortName>Income Taxes (Cash Income Taxes Paid, Net of Amounts Refunded) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxesTables</ParentRole>
      <Position>102</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>9955577 - Disclosure - Income Taxes (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/IncomeTaxesNarrativeDetails</Role>
      <ShortName>Income Taxes (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/IncomeTaxesTables</ParentRole>
      <Position>103</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>9955578 - Disclosure - Pension And Postretirement Benefits (Change In The Projected Benefit Obligation) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsChangeInTheProjectedBenefitObligationDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Change In The Projected Benefit Obligation) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>104</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>9955579 - Disclosure - Pension And Postretirement Benefits (Change In The Value Of Plan Assets And The Plans' Funded Status) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsChangeInTheValueOfPlanAssetsAndThePlansFundedStatusDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Change In The Value Of Plan Assets And The Plans' Funded Status) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>105</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>9955580 - Disclosure - Pension And Postretirement Benefits (Employee Benefit Obligation Amounts Recognized) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsEmployeeBenefitObligationAmountsRecognizedDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Employee Benefit Obligation Amounts Recognized) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>106</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>9955581 - Disclosure - Pension And Postretirement Benefits (Net Periodic Benefit Cost (Credit)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsNetPeriodicBenefitCostCreditDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Net Periodic Benefit Cost (Credit)) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>107</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>9955582 - Disclosure - Pension And Postretirement Benefits (Other Changes Recognized in Other Comprehensive Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsOtherChangesRecognizedinOtherComprehensiveIncomeDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Other Changes Recognized in Other Comprehensive Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>108</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>9955583 - Disclosure - Pension and Postretirement Benefits (Weighted Average Assumptions - Projected Benefit Obligation And Net Pension And Postemployment Benefit Cost) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionandPostretirementBenefitsWeightedAverageAssumptionsProjectedBenefitObligationAndNetPensionAndPostemploymentBenefitCostDetails</Role>
      <ShortName>Pension and Postretirement Benefits (Weighted Average Assumptions - Projected Benefit Obligation And Net Pension And Postemployment Benefit Cost) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>9955584 - Disclosure - Pension And Postretirement Benefits (Schedule Of Defined Benefit Plan Targeted And Actual Plan Asset Allocations) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsScheduleOfDefinedBenefitPlanTargetedAndActualPlanAssetAllocationsDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Schedule Of Defined Benefit Plan Targeted And Actual Plan Asset Allocations) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>110</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>9955585 - Disclosure - Pension And Postretirement Benefits (Schedule Of Fair Value Of Pension And Postretirement Assets And Liabilities By Level) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsScheduleOfFairValueOfPensionAndPostretirementAssetsAndLiabilitiesByLevelDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Schedule Of Fair Value Of Pension And Postretirement Assets And Liabilities By Level) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>111</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>9955586 - Disclosure - Pension And Postretirement Benefits (Fair Value Assets Measured On Recurring Basis Unobservable Input (Level 3) Reconciliation) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsFairValueAssetsMeasuredOnRecurringBasisUnobservableInputLevel3ReconciliationDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Fair Value Assets Measured On Recurring Basis Unobservable Input (Level 3) Reconciliation) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>112</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>9955587 - Disclosure - Pension And Postretirement Benefits (Estimated Future Benefit Payments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsEstimatedFutureBenefitPaymentsDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Estimated Future Benefit Payments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>113</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>9955588 - Disclosure - Pension And Postretirement Benefits (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/PensionAndPostretirementBenefitsNarrativeDetails</Role>
      <ShortName>Pension And Postretirement Benefits (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/PensionAndPostretirementBenefitsTables</ParentRole>
      <Position>114</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>9955589 - Disclosure - Share-Based Payments (Compensation Cost And Valuation Assumption) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ShareBasedPaymentsCompensationCostAndValuationAssumptionDetails</Role>
      <ShortName>Share-Based Payments (Compensation Cost And Valuation Assumption) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/ShareBasedPaymentsTables</ParentRole>
      <Position>115</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R116.htm</HtmlFileName>
      <LongName>9955590 - Disclosure - Share-Based Payments (Summary Of Nonvested Stock Units Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ShareBasedPaymentsSummaryOfNonvestedStockUnitsActivityDetails</Role>
      <ShortName>Share-Based Payments (Summary Of Nonvested Stock Units Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/ShareBasedPaymentsTables</ParentRole>
      <Position>116</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>9955591 - Disclosure - Share-Based Payments (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ShareBasedPaymentsNarrativeDetails</Role>
      <ShortName>Share-Based Payments (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/ShareBasedPaymentsTables</ParentRole>
      <Position>117</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R118.htm</HtmlFileName>
      <LongName>9955592 - Disclosure - Stockholders' and Mezzanine Equity (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/StockholdersandMezzanineEquityNarrativeDetails</Role>
      <ShortName>Stockholders' and Mezzanine Equity (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/StockholdersandMezzanineEquity</ParentRole>
      <Position>118</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R119.htm</HtmlFileName>
      <LongName>9955593 - Disclosure - Stockholders' and Mezzanine Equity (Preferred Interest Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/StockholdersandMezzanineEquityPreferredInterestNarrativeDetails</Role>
      <ShortName>Stockholders' and Mezzanine Equity (Preferred Interest Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/StockholdersandMezzanineEquity</ParentRole>
      <Position>119</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R120.htm</HtmlFileName>
      <LongName>9955594 - Disclosure - Sales Of Receivables (Summary of Cash Proceeds Received from Sale of Receivables) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivablesSummaryofCashProceedsReceivedfromSaleofReceivablesDetails</Role>
      <ShortName>Sales Of Receivables (Summary of Cash Proceeds Received from Sale of Receivables) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SalesOfReceivablesTables</ParentRole>
      <Position>120</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R121.htm</HtmlFileName>
      <LongName>9955595 - Disclosure - Sales Of Receivables (Equipment Installment and AT&amp;T Revolving Programs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivablesEquipmentInstallmentandATTRevolvingProgramsDetails</Role>
      <ShortName>Sales Of Receivables (Equipment Installment and AT&amp;T Revolving Programs) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SalesOfReceivablesTables</ParentRole>
      <Position>121</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R122.htm</HtmlFileName>
      <LongName>9955596 - Disclosure - Sales Of Receivables (Finance Receivables) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivablesFinanceReceivablesDetails</Role>
      <ShortName>Sales Of Receivables (Finance Receivables) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SalesOfReceivablesTables</ParentRole>
      <Position>122</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R123.htm</HtmlFileName>
      <LongName>9955597 - Disclosure - Sales Of Receivables (Finance Receivables Repurchased) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivablesFinanceReceivablesRepurchasedDetails</Role>
      <ShortName>Sales Of Receivables (Finance Receivables Repurchased) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SalesOfReceivablesTables</ParentRole>
      <Position>123</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R124.htm</HtmlFileName>
      <LongName>9955598 - Disclosure - Sales Of Receivables (Revolving Receivables Sold) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivablesRevolvingReceivablesSoldDetails</Role>
      <ShortName>Sales Of Receivables (Revolving Receivables Sold) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SalesOfReceivablesTables</ParentRole>
      <Position>124</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R125.htm</HtmlFileName>
      <LongName>9955599 - Disclosure - Sales Of Receivables (Equipment Installment and AT&amp;T Revolving Programs) (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SalesOfReceivablesEquipmentInstallmentandATTRevolvingProgramsNarrativeDetails</Role>
      <ShortName>Sales Of Receivables (Equipment Installment and AT&amp;T Revolving Programs) (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SalesOfReceivablesTables</ParentRole>
      <Position>125</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R126.htm</HtmlFileName>
      <LongName>9955600 - Disclosure - Tower Transaction (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/TowerTransactionNarrativeDetails</Role>
      <ShortName>Tower Transaction (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/TowerTransaction</ParentRole>
      <Position>126</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R127.htm</HtmlFileName>
      <LongName>9955601 - Disclosure - Transactions With DIRECTV (Equity Income and Cash Distributions) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/TransactionsWithDIRECTVEquityIncomeandCashDistributionsDetails</Role>
      <ShortName>Transactions With DIRECTV (Equity Income and Cash Distributions) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/TransactionsWithDIRECTVDisclosures</ParentRole>
      <Position>127</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R128.htm</HtmlFileName>
      <LongName>9955602 - Disclosure - Transactions With DIRECTV (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/TransactionsWithDIRECTVNarrativeDetails</Role>
      <ShortName>Transactions With DIRECTV (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/TransactionsWithDIRECTVDisclosures</ParentRole>
      <Position>128</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R129.htm</HtmlFileName>
      <LongName>9955603 - Disclosure - FirstNet (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/FirstNetNarrativeDetails</Role>
      <ShortName>FirstNet (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/FirstNet</ParentRole>
      <Position>129</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R130.htm</HtmlFileName>
      <LongName>9955604 - Disclosure - Contingent Liabilities (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ContingentLiabilitiesNarrativeDetails</Role>
      <ShortName>Contingent Liabilities (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/ContingentLiabilities</ParentRole>
      <Position>130</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R131.htm</HtmlFileName>
      <LongName>9955605 - Disclosure - Supplier and Vendor Financing Programs (Supplier Financing) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SupplierandVendorFinancingProgramsSupplierFinancingDetails</Role>
      <ShortName>Supplier and Vendor Financing Programs (Supplier Financing) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SupplierandVendorFinancingProgramsTables</ParentRole>
      <Position>131</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R132.htm</HtmlFileName>
      <LongName>9955606 - Disclosure - Supplier and Vendor Financing Programs (Vendor Financing) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/SupplierandVendorFinancingProgramsVendorFinancingDetails</Role>
      <ShortName>Supplier and Vendor Financing Programs (Vendor Financing) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/SupplierandVendorFinancingProgramsTables</ParentRole>
      <Position>132</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R133.htm</HtmlFileName>
      <LongName>9955607 - Disclosure - Additional Financial Information (Consolidated Balance Sheets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AdditionalFinancialInformationConsolidatedBalanceSheetsDetails</Role>
      <ShortName>Additional Financial Information (Consolidated Balance Sheets) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/AdditionalFinancialInformationTables</ParentRole>
      <Position>133</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R134.htm</HtmlFileName>
      <LongName>9955608 - Disclosure - Additional Financial Information (Consolidated Statements Of Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AdditionalFinancialInformationConsolidatedStatementsOfIncomeDetails</Role>
      <ShortName>Additional Financial Information (Consolidated Statements Of Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/AdditionalFinancialInformationTables</ParentRole>
      <Position>134</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R135.htm</HtmlFileName>
      <LongName>9955609 - Disclosure - Additional Financial Information (Cash and Cash Equivalents and Restricted Cash) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AdditionalFinancialInformationCashandCashEquivalentsandRestrictedCashDetails</Role>
      <ShortName>Additional Financial Information (Cash and Cash Equivalents and Restricted Cash) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/AdditionalFinancialInformationTables</ParentRole>
      <Position>135</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R136.htm</HtmlFileName>
      <LongName>9955610 - Disclosure - Additional Financial Information (Consolidated Statements Of Cash Flows) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AdditionalFinancialInformationConsolidatedStatementsOfCashFlowsDetails</Role>
      <ShortName>Additional Financial Information (Consolidated Statements Of Cash Flows) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/AdditionalFinancialInformationTables</ParentRole>
      <Position>136</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R137.htm</HtmlFileName>
      <LongName>9955611 - Disclosure - Additional Financial Information (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/AdditionalFinancialInformationNarrativeDetails</Role>
      <ShortName>Additional Financial Information (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://att.com/role/AdditionalFinancialInformationTables</ParentRole>
      <Position>137</Position>
    </Report>
    <Report instance="t-20251231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R138.htm</HtmlFileName>
      <LongName>9955612 - Disclosure - Valuation And Qualifying Accounts (Allowance For Doubtful Accounts) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://att.com/role/ValuationAndQualifyingAccountsAllowanceForDoubtfulAccountsDetails</Role>
      <ShortName>Valuation And Qualifying Accounts (Allowance For Doubtful Accounts) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>138</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-K" isDefinitelyFs="true" isUsgaap="true" original="t-20251231.htm">t-20251231.htm</File>
    <File>t-20251231.xsd</File>
    <File>t-20251231_cal.xml</File>
    <File>t-20251231_def.xml</File>
    <File>t-20251231_lab.xml</File>
    <File>t-20251231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>t-20251231_g1.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="3">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="2523">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="16">http://xbrl.sec.gov/cyd/2025</BaseTaxonomy>
    <BaseTaxonomy items="140">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
