<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>791</ContextCount>
  <ElementCount>438</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>126</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>10</UnitCount>
  <MyReports>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/CONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/CONSOLIDATEDBALANCESHEETSParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/CONSOLIDATEDSTATEMENTSOFINCOME</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITY</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITYParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="zions-20260331.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://www.zionsbancorp.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Disclosure - BASIS OF PRESENTATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/BASISOFPRESENTATION</Role>
      <ShortName>BASIS OF PRESENTATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - RECENT ACCOUNTING PRONOUNCEMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/RECENTACCOUNTINGPRONOUNCEMENTS</Role>
      <ShortName>RECENT ACCOUNTING PRONOUNCEMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - FAIR VALUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/FAIRVALUE</Role>
      <ShortName>FAIR VALUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIES</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - INVESTMENT SECURITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INVESTMENTSECURITIES</Role>
      <ShortName>INVESTMENT SECURITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSES</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LEASES</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - LONG-TERM DEBT AND SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITY</Role>
      <ShortName>LONG-TERM DEBT AND SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/COMMITMENTSGUARANTEESANDCONTINGENTLIABILITIES</Role>
      <ShortName>COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERS</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INCOMETAXES</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - NET EARNINGS PER COMMON SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/NETEARNINGSPERCOMMONSHARE</Role>
      <ShortName>NET EARNINGS PER COMMON SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - OPERATING SEGMENT INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/OPERATINGSEGMENTINFORMATION</Role>
      <ShortName>OPERATING SEGMENT INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.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>22</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - RECENT ACCOUNTING PRONOUNCEMENTS (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/RECENTACCOUNTINGPRONOUNCEMENTSPolicies</Role>
      <ShortName>RECENT ACCOUNTING PRONOUNCEMENTS (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - RECENT ACCOUNTING PRONOUNCEMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/RECENTACCOUNTINGPRONOUNCEMENTSTables</Role>
      <ShortName>RECENT ACCOUNTING PRONOUNCEMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/RECENTACCOUNTINGPRONOUNCEMENTS</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - FAIR VALUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/FAIRVALUETables</Role>
      <ShortName>FAIR VALUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/FAIRVALUE</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESTables</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIES</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - INVESTMENT SECURITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESTables</Role>
      <ShortName>INVESTMENT SECURITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/INVESTMENTSECURITIES</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSES</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LEASESTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LEASES</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYTables</Role>
      <ShortName>LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITY</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/COMMITMENTSGUARANTEESANDCONTINGENTLIABILITIESTables</Role>
      <ShortName>COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/COMMITMENTSGUARANTEESANDCONTINGENTLIABILITIES</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSTables</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERS</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - NET EARNINGS PER COMMON SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/NETEARNINGSPERCOMMONSHARETables</Role>
      <ShortName>NET EARNINGS PER COMMON SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/NETEARNINGSPERCOMMONSHARE</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - OPERATING SEGMENT INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/OPERATINGSEGMENTINFORMATIONTables</Role>
      <ShortName>OPERATING SEGMENT INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/OPERATINGSEGMENTINFORMATION</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - BASIS OF PRESENTATION (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/BASISOFPRESENTATIONDetails</Role>
      <ShortName>BASIS OF PRESENTATION (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/BASISOFPRESENTATION</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - FAIR VALUE (Schedule of Assets and Liabilities Measured at Fair Value by Class on a Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/FAIRVALUEScheduleofAssetsandLiabilitiesMeasuredatFairValuebyClassonaRecurringBasisDetails</Role>
      <ShortName>FAIR VALUE (Schedule of Assets and Liabilities Measured at Fair Value by Class on a Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/FAIRVALUETables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - FAIR VALUE (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/FAIRVALUENarrativeDetails</Role>
      <ShortName>FAIR VALUE (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/FAIRVALUETables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - FAIR VALUE (Schedule of Assets and Liabilities Measured at Fair Value by Class on a Recurring Basis Using Level 3 Inputs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/FAIRVALUEScheduleofAssetsandLiabilitiesMeasuredatFairValuebyClassonaRecurringBasisUsingLevel3InputsDetails</Role>
      <ShortName>FAIR VALUE (Schedule of Assets and Liabilities Measured at Fair Value by Class on a Recurring Basis Using Level 3 Inputs) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/FAIRVALUETables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - FAIR VALUE (Schedule of Rollforward of Level 3 Fair Value Measurements Including Realized Gains and Losses in the Income Statement) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/FAIRVALUEScheduleofRollforwardofLevel3FairValueMeasurementsIncludingRealizedGainsandLossesintheIncomeStatementDetails</Role>
      <ShortName>FAIR VALUE (Schedule of Rollforward of Level 3 Fair Value Measurements Including Realized Gains and Losses in the Income Statement) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/FAIRVALUETables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - FAIR VALUE (Schedule of Carrying Values and Estimated Fair Values of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/FAIRVALUEScheduleofCarryingValuesandEstimatedFairValuesofFinancialInstrumentsDetails</Role>
      <ShortName>FAIR VALUE (Schedule of Carrying Values and Estimated Fair Values of Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/FAIRVALUETables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESNarrativeDetails</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Notional and Recorded Fair Values) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESNotionalandRecordedFairValuesDetails</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Notional and Recorded Fair Values) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Derivative Gain (Loss) Recognized/Reclassified) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESDerivativeGainLossRecognizedReclassifiedDetails</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Derivative Gain (Loss) Recognized/Reclassified) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Derivatives Not Designated as Hedges) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESDerivativesNotDesignatedasHedgesDetails</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Derivatives Not Designated as Hedges) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Gain (Loss) Recorded in Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESGainLossRecordedinIncomeDetails</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Gain (Loss) Recorded in Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Basis Adjustments for Hedged Items) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESBasisAdjustmentsforHedgedItemsDetails</Role>
      <ShortName>DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Basis Adjustments for Hedged Items) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/DERIVATIVEINSTRUMENTSANDHEDGINGACTIVITIESTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - INVESTMENT SECURITIES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESNarrativeDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - INVESTMENT SECURITIES (Summary of Investment Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESSummaryofInvestmentSecuritiesDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Summary of Investment Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - INVESTMENT SECURITIES (Summary of Amount of Gross Unrealized Losses for Debt Securities and Estimated Fair Value) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESSummaryofAmountofGrossUnrealizedLossesforDebtSecuritiesandEstimatedFairValueDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Summary of Amount of Gross Unrealized Losses for Debt Securities and Estimated Fair Value) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - INVESTMENT SECURITIES (Schedule of Investment Securities, Taxable and Nontaxable) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESScheduleofInvestmentSecuritiesTaxableandNontaxableDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Schedule of Investment Securities, Taxable and Nontaxable) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - INVESTMENT SECURITIES (Contractual Maturities Debt Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESContractualMaturitiesDebtSecuritiesDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Contractual Maturities Debt Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/INVESTMENTSECURITIESTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Major Portfolio Segment and Specific Loan Class) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofMajorPortfolioSegmentandSpecificLoanClassDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Major Portfolio Segment and Specific Loan Class) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESNarrativeDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Loans Held For Sale) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESLoansHeldForSaleDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Loans Held For Sale) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Changes in the Allowance for Credit Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofChangesintheAllowanceforCreditLossesDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Changes in the Allowance for Credit Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Nonaccrual Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofNonaccrualLoansDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Nonaccrual Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Accrued Interest Receivables Reversed) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofAccruedInterestReceivablesReversedDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Accrued Interest Receivables Reversed) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Past Due Loans (Accruing and Nonaccruing)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofPastDueLoansAccruingandNonaccruingDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Past Due Loans (Accruing and Nonaccruing)) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Outstanding Loan Balances (Accruing and Nonaccruing) Categorized by Credit Quality Indicators - Current Year) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofOutstandingLoanBalancesAccruingandNonaccruingCategorizedbyCreditQualityIndicatorsCurrentYearDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Outstanding Loan Balances (Accruing and Nonaccruing) Categorized by Credit Quality Indicators - Current Year) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Outstanding Loan Balances (Accruing and Nonaccruing) Categorized by Credit Quality Indicators - Prior Year) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofOutstandingLoanBalancesAccruingandNonaccruingCategorizedbyCreditQualityIndicatorsPriorYearDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Outstanding Loan Balances (Accruing and Nonaccruing) Categorized by Credit Quality Indicators - Prior Year) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Selected Information on Modified Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofSelectedInformationonModifiedLoansDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Selected Information on Modified Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Financial Impact of Loan Modifications) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryofFinancialImpactofLoanModificationsDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Financial Impact of Loan Modifications) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary Aging Analysis, Modified) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESSummaryAgingAnalysisModifiedDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary Aging Analysis, Modified) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Collateral-Dependent Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESCollateralDependentLoansDetails</Role>
      <ShortName>LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Collateral-Dependent Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LOANSLEASESANDALLOWANCEFORCREDITLOSSESTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - LEASES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LEASESNarrativeDetails</Role>
      <ShortName>LEASES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LEASESTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - LEASES (Assets and Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LEASESAssetsandLiabilitiesDetails</Role>
      <ShortName>LEASES (Assets and Liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LEASESTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - LEASES (Components of Lease Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LEASESComponentsofLeaseExpenseDetails</Role>
      <ShortName>LEASES (Components of Lease Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LEASESTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - LEASES (Maturities Analysis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LEASESMaturitiesAnalysisDetails</Role>
      <ShortName>LEASES (Maturities Analysis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LEASESTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Long-term Debt) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYLongtermDebtDetails</Role>
      <ShortName>LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Long-term Debt) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYNarrativeDetails</Role>
      <ShortName>LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYTables</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Changes In Accumulated Other Comprehensive Income (Loss)) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYChangesInAccumulatedOtherComprehensiveIncomeLossDetails</Role>
      <ShortName>LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Changes In Accumulated Other Comprehensive Income (Loss)) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYTables</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Amounts Reclassified from AOCI) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYAmountsReclassifiedfromAOCIDetails</Role>
      <ShortName>LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Amounts Reclassified from AOCI) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/LONGTERMDEBTANDSHAREHOLDERSEQUITYTables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES (Schedule of Off Balance Sheet Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/COMMITMENTSGUARANTEESANDCONTINGENTLIABILITIESScheduleofOffBalanceSheetFinancialInstrumentsDetails</Role>
      <ShortName>COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES (Schedule of Off Balance Sheet Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/COMMITMENTSGUARANTEESANDCONTINGENTLIABILITIESTables</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/COMMITMENTSGUARANTEESANDCONTINGENTLIABILITIESNarrativeDetails</Role>
      <ShortName>COMMITMENTS, GUARANTEES AND CONTINGENT LIABILITIES (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/COMMITMENTSGUARANTEESANDCONTINGENTLIABILITIESTables</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSDetails</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSTables</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9955564 - Disclosure - INCOME TAXES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/INCOMETAXESDetails</Role>
      <ShortName>INCOME TAXES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/INCOMETAXES</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9955565 - Disclosure - NET EARNINGS PER COMMON SHARE - Basic and Diluted Net Earnings Per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/NETEARNINGSPERCOMMONSHAREBasicandDilutedNetEarningsPerCommonShareDetails</Role>
      <ShortName>NET EARNINGS PER COMMON SHARE - Basic and Diluted Net Earnings Per Common Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9955566 - Disclosure - NET EARNINGS PER COMMON SHARE - Stock Awards that were Anti-Dilutive (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/NETEARNINGSPERCOMMONSHAREStockAwardsthatwereAntiDilutiveDetails</Role>
      <ShortName>NET EARNINGS PER COMMON SHARE - Stock Awards that were Anti-Dilutive (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9955567 - Disclosure - OPERATING SEGMENT INFORMATION (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/OPERATINGSEGMENTINFORMATIONNarrativeDetails</Role>
      <ShortName>OPERATING SEGMENT INFORMATION (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/OPERATINGSEGMENTINFORMATIONTables</ParentRole>
      <Position>79</Position>
    </Report>
    <Report instance="zions-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9955568 - Disclosure - OPERATING SEGMENT INFORMATION (Schedule Of Segment Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.zionsbancorp.com/role/OPERATINGSEGMENTINFORMATIONScheduleOfSegmentInformationDetails</Role>
      <ShortName>OPERATING SEGMENT INFORMATION (Schedule Of Segment Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.zionsbancorp.com/role/OPERATINGSEGMENTINFORMATIONTables</ParentRole>
      <Position>80</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-Q" isDefinitelyFs="true" isUsgaap="true" original="zions-20260331.htm">zions-20260331.htm</File>
    <File>zions-20260331.xsd</File>
    <File>zions-20260331_cal.xml</File>
    <File>zions-20260331_def.xml</File>
    <File>zions-20260331_lab.xml</File>
    <File>zions-20260331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>zions-20260331_g1.jpg</File>
    <File>zions-20260331_g10.jpg</File>
    <File>zions-20260331_g11.jpg</File>
    <File>zions-20260331_g12.jpg</File>
    <File>zions-20260331_g13.jpg</File>
    <File>zions-20260331_g2.jpg</File>
    <File>zions-20260331_g3.jpg</File>
    <File>zions-20260331_g4.jpg</File>
    <File>zions-20260331_g5.jpg</File>
    <File>zions-20260331_g6.jpg</File>
    <File>zions-20260331_g7.jpg</File>
    <File>zions-20260331_g8.jpg</File>
    <File>zions-20260331_g9.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="3129">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="32">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
