<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>618</ContextCount>
  <ElementCount>537</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>123</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Document and Entity Information Document</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DocumentandEntityInformationDocument</Role>
      <ShortName>Document and Entity Information Document</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="cbsh-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.commercebank.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="cbsh-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.commercebank.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="cbsh-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.commercebank.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>Consolidated Statements Of Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="cbsh-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.commercebank.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements Of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - Consolidated Statements Of Changes In Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ConsolidatedStatementsOfChangesInEquity</Role>
      <ShortName>Consolidated Statements Of Changes In Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Statement - Consolidated Statements Of Changes In Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ConsolidatedStatementsOfChangesInEquityParenthetical</Role>
      <ShortName>Consolidated Statements Of Changes In Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="cbsh-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.commercebank.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements Of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Statement - Consolidated Statements Of Cash Flows Cash Flow Additional Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ConsolidatedStatementsOfCashFlowsCashFlowAdditionalInformation</Role>
      <ShortName>Consolidated Statements Of Cash Flows Cash Flow Additional Information</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - Principles Of Consolidation And Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/PrinciplesOfConsolidationAndPresentation</Role>
      <ShortName>Principles Of Consolidation And Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Acquisition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/Acquisition</Role>
      <ShortName>Acquisition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Loans And Allowance For Credit Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLosses</Role>
      <ShortName>Loans And Allowance For Credit Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - Investment Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecurities</Role>
      <ShortName>Investment Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Goodwill And Other Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssets</Role>
      <ShortName>Goodwill And Other Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Guarantees</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/Guarantees</Role>
      <ShortName>Guarantees</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Pension</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/Pension</Role>
      <ShortName>Pension</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Common Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/CommonStock</Role>
      <ShortName>Common Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Accumulated Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AccumulatedOtherComprehensiveIncome</Role>
      <ShortName>Accumulated Other Comprehensive Income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - Segments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/Segments</Role>
      <ShortName>Segments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - Derivative Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstruments</Role>
      <ShortName>Derivative Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9952171 - Disclosure - Resale and Repurchase Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ResaleandRepurchaseAgreements</Role>
      <ShortName>Resale and Repurchase Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9952172 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/StockBasedCompensation</Role>
      <ShortName>Stock-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9952173 - Disclosure - Revenue from Contract with Customer</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/RevenuefromContractwithCustomer</Role>
      <ShortName>Revenue from Contract with Customer</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9952174 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9952175 - Disclosure - Fair Value Of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueOfFinancialInstruments</Role>
      <ShortName>Fair Value Of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9952176 - Disclosure - Legal and Regulatory Proceedings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LegalandRegulatoryProceedings</Role>
      <ShortName>Legal and Regulatory Proceedings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.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>28</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - Acquisition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AcquisitionTables</Role>
      <ShortName>Acquisition (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/Acquisition</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - Loans And Allowance For Credit Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</Role>
      <ShortName>Loans And Allowance For Credit Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLosses</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - Investment Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecuritiesTables</Role>
      <ShortName>Investment Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/InvestmentSecurities</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - Goodwill And Other Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsTables</Role>
      <ShortName>Goodwill And Other Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssets</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/Leases</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - Pension (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/PensionTables</Role>
      <ShortName>Pension (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/Pension</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - Common Stock (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/CommonStockTables</Role>
      <ShortName>Common Stock (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/CommonStock</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - Accumulated Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AccumulatedOtherComprehensiveIncomeTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/AccumulatedOtherComprehensiveIncome</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - Segments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/SegmentsTables</Role>
      <ShortName>Segments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/Segments</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - Derivative Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsTables</Role>
      <ShortName>Derivative Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstruments</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - Resale and Repurchase Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ResaleandRepurchaseAgreementsTables</Role>
      <ShortName>Resale and Repurchase Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/ResaleandRepurchaseAgreements</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - Stock-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/StockBasedCompensationTables</Role>
      <ShortName>Stock-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/StockBasedCompensation</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - Revenue from Contracts with Customers (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/RevenuefromContractswithCustomersTables</Role>
      <ShortName>Revenue from Contracts with Customers (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueMeasurements</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - Fair Value Of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueOfFinancialInstrumentsTables</Role>
      <ShortName>Fair Value Of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueOfFinancialInstruments</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - Acquisition (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AcquisitionNarrativeDetails</Role>
      <ShortName>Acquisition (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/AcquisitionTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - Acquisition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AcquisitionDetails</Role>
      <ShortName>Acquisition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/AcquisitionTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - Acquisition (Acquired Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AcquisitionAcquiredLoansDetails</Role>
      <ShortName>Acquisition (Acquired Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/AcquisitionTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - Acquisition (Pro Forma Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AcquisitionProFormaInformationDetails</Role>
      <ShortName>Acquisition (Pro Forma Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/AcquisitionTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - Loans And Allowance For Credit Losses (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesNarrativeDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - Loans And Allowance For Credit Losses (Summary Classification Of Held To Maturity Loan Portfolio) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesSummaryClassificationOfHeldToMaturityLoanPortfolioDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Summary Classification Of Held To Maturity Loan Portfolio) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - Loans And Allowance For Credit Losses (Summary of Activity in the Allowance for Credit Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesSummaryofActivityintheAllowanceforCreditLossesDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Summary of Activity in the Allowance for Credit Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - Loans And Allowance For Credit Losses (Aging Information On Past Due And Accruing Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesAgingInformationOnPastDueAndAccruingLoansDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Aging Information On Past Due And Accruing Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - Loans And Allowance For Credit Losses (Credit Quality Indicators Commercial Loan Portfolio) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesCreditQualityIndicatorsCommercialLoanPortfolioDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Credit Quality Indicators Commercial Loan Portfolio) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - Loans And Allowance for Credit Losses (Credit Quality Indicators Personal Banking Loan Portfolio) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceforCreditLossesCreditQualityIndicatorsPersonalBankingLoanPortfolioDetails</Role>
      <ShortName>Loans And Allowance for Credit Losses (Credit Quality Indicators Personal Banking Loan Portfolio) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - Loans And Allowance for Credit Losses (Collateral-Dependent Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceforCreditLossesCollateralDependentLoansDetails</Role>
      <ShortName>Loans And Allowance for Credit Losses (Collateral-Dependent Loans) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - Loans And Allowance For Credit Losses (Financial Impacts of Loan Modifications) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesFinancialImpactsofLoanModificationsDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Financial Impacts of Loan Modifications) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - Loans And Allowance For Credit Losses (Modified Amortized Cost) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesModifiedAmortizedCostDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Modified Amortized Cost) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - Loans And Allowance For Credit Losses (Amortized Cost Basis of Loans to Borrowers with Financial Difficulty with a Payment Default) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesAmortizedCostBasisofLoanstoBorrowerswithFinancialDifficultywithaPaymentDefaultDetails</Role>
      <ShortName>Loans And Allowance For Credit Losses (Amortized Cost Basis of Loans to Borrowers with Financial Difficulty with a Payment Default) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - Loans And Allowance For Credit Losses (Amortized Cost Basis of Loans Modified After Adoption of ASU 2022-02) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesAmortizedCostBasisofLoansModifiedAfterAdoptionofASU202202Details</Role>
      <ShortName>Loans And Allowance For Credit Losses (Amortized Cost Basis of Loans Modified After Adoption of ASU 2022-02) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LoansAndAllowanceForCreditLossesTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - Investment Securities (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecuritiesNarrativeDetails</Role>
      <ShortName>Investment Securities (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - Investment Securities (Investment Securities, At Fair Value) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecuritiesInvestmentSecuritiesAtFairValueDetails</Role>
      <ShortName>Investment Securities (Investment Securities, At Fair Value) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecuritiesSummaryOfAvailableForSaleInvestmentSecuritiesByMaturityGroupingsDetails</Role>
      <ShortName>Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecuritiesSecuritiesWithUnrealizedLossesAndLengthOfImpairmentPeriodDetails</Role>
      <ShortName>Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecuritiesAvailableForSaleSecuritiesUnrealizedGainsAndLossesBySecurityTypeDetails</Role>
      <ShortName>Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - Investment Securities (Proceeds From Sales Of Securities And Components Of Investment Securities Gains And Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/InvestmentSecuritiesProceedsFromSalesOfSecuritiesAndComponentsOfInvestmentSecuritiesGainsAndLossesDetails</Role>
      <ShortName>Investment Securities (Proceeds From Sales Of Securities And Components Of Investment Securities Gains And Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - Goodwill And Other Intangible Assets (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsNarrativeDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - Goodwill And Other Intangible Assets (Schedule Of Intangible Assets With Estimable Useful Lives) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfIntangibleAssetsWithEstimableUsefulLivesDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Schedule Of Intangible Assets With Estimable Useful Lives) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - Goodwill And Other Intangible Assets (Schedule Of Estimated Annual Amortization Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfEstimatedAnnualAmortizationExpenseDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Schedule Of Estimated Annual Amortization Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - Goodwill And Other Intangible Assets (Schedule Of Changes In Carrying Amount Of Goodwill And Net Other Intangible Assets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfChangesInCarryingAmountOfGoodwillAndNetOtherIntangibleAssetsDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Schedule Of Changes In Carrying Amount Of Goodwill And Net Other Intangible Assets) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - Goodwill And Other Intangible Assets (Schedule Of Goodwill Allocated By Operating Segments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfGoodwillAllocatedByOperatingSegmentsDetails</Role>
      <ShortName>Goodwill And Other Intangible Assets (Schedule Of Goodwill Allocated By Operating Segments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/GoodwillAndOtherIntangibleAssetsTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - Guarantees (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/GuaranteesDetails</Role>
      <ShortName>Guarantees (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/Guarantees</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - Leases (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LeasesNarrativeDetails</Role>
      <ShortName>Leases (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LeasesTables</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - Leases (Components of Lease Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/LeasesComponentsofLeaseIncomeDetails</Role>
      <ShortName>Leases (Components of Lease Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/LeasesTables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - Pension (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/PensionNarrativeDetails</Role>
      <ShortName>Pension (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/PensionTables</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - Pension (Net Pension Cost) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/PensionNetPensionCostDetails</Role>
      <ShortName>Pension (Net Pension Cost) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/PensionTables</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - Common Stock (Summary Of Components Used To Calculate Basic And Diluted Income Per Share) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/CommonStockSummaryOfComponentsUsedToCalculateBasicAndDilutedIncomePerShareDetails</Role>
      <ShortName>Common Stock (Summary Of Components Used To Calculate Basic And Diluted Income Per Share) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/CommonStockTables</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - Common Stock (AntiDilutive Securities Excluded from Computation of Earnings per Share) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/CommonStockAntiDilutiveSecuritiesExcludedfromComputationofEarningsperShareDetails</Role>
      <ShortName>Common Stock (AntiDilutive Securities Excluded from Computation of Earnings per Share) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/CommonStockTables</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/AccumulatedOtherComprehensiveIncomeScheduleOfAccumulatedOtherComprehensiveIncomeDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/AccumulatedOtherComprehensiveIncomeTables</ParentRole>
      <Position>77</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - Segments (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/SegmentsNarrativeDetails</Role>
      <ShortName>Segments (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/SegmentsTables</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - Segments (Schedule Of Financial Information By Segment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/SegmentsScheduleOfFinancialInformationBySegmentDetails</Role>
      <ShortName>Segments (Schedule Of Financial Information By Segment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/SegmentsTables</ParentRole>
      <Position>79</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9955564 - Disclosure - Derivative Instruments (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsNarrativeDetails</Role>
      <ShortName>Derivative Instruments (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9955565 - Disclosure - Derivative Instruments (Schedule Of Notional Amounts Of Derivative Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsScheduleOfNotionalAmountsOfDerivativeInstrumentsDetails</Role>
      <ShortName>Derivative Instruments (Schedule Of Notional Amounts Of Derivative Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9955566 - Disclosure - Schedule of Gains/Losses on Fair Value Hedge (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ScheduleofGainsLossesonFairValueHedgeDetails</Role>
      <ShortName>Schedule of Gains/Losses on Fair Value Hedge (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9955567 - Disclosure - Derivative Instruments (Interest Rate Floor Summary) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsInterestRateFloorSummaryDetails</Role>
      <ShortName>Derivative Instruments (Interest Rate Floor Summary) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9955568 - Disclosure - Derivative Instruments (Schedule Of Fair Values Of Derivative Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsScheduleOfFairValuesOfDerivativeInstrumentsDetails</Role>
      <ShortName>Derivative Instruments (Schedule Of Fair Values Of Derivative Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9955569 - Disclosure - Derivative Instruments (Summary of Cash Flow Hedge Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsSummaryofCashFlowHedgeActivityDetails</Role>
      <ShortName>Derivative Instruments (Summary of Cash Flow Hedge Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9955570 - Disclosure - Derivative Instruments (Summary Of The Effects Of Derivative Instruments On Consolidated Statements Of Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsSummaryOfTheEffectsOfDerivativeInstrumentsOnConsolidatedStatementsOfIncomeDetails</Role>
      <ShortName>Derivative Instruments (Summary Of The Effects Of Derivative Instruments On Consolidated Statements Of Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9955571 - Disclosure - Derivative Instruments (Balance Sheet Offsetting) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/DerivativeInstrumentsBalanceSheetOffsettingDetails</Role>
      <ShortName>Derivative Instruments (Balance Sheet Offsetting) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9955573 - Disclosure - Resale and Repurchase Agreements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ResaleandRepurchaseAgreementsDetails</Role>
      <ShortName>Resale and Repurchase Agreements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/ResaleandRepurchaseAgreementsTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>9955574 - Disclosure - Resale and Repurchase Agreements Remaining Contractual Maturities of Repurchase Agreements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/ResaleandRepurchaseAgreementsRemainingContractualMaturitiesofRepurchaseAgreementsDetails</Role>
      <ShortName>Resale and Repurchase Agreements Remaining Contractual Maturities of Repurchase Agreements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>9955575 - Disclosure - Stock-Based Compensation (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/StockBasedCompensationNarrativeDetails</Role>
      <ShortName>Stock-Based Compensation (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/StockBasedCompensationTables</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>9955576 - Disclosure - Stock-Based Compensation (Summary Of The Status Of Nonvested Share Awards) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/StockBasedCompensationSummaryOfTheStatusOfNonvestedShareAwardsDetails</Role>
      <ShortName>Stock-Based Compensation (Summary Of The Status Of Nonvested Share Awards) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/StockBasedCompensationTables</ParentRole>
      <Position>91</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>9955577 - Disclosure - Stock-Based Compensation (Schedule of Nonvested Restricted and Performance Stock Units Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/StockBasedCompensationScheduleofNonvestedRestrictedandPerformanceStockUnitsActivityDetails</Role>
      <ShortName>Stock-Based Compensation (Schedule of Nonvested Restricted and Performance Stock Units Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/StockBasedCompensationTables</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>9955578 - Disclosure - Stock-Based Compensation Stock-Based Compensation (Current Year Per Share Average Fair Value and Valuation Model Assumptions) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/StockBasedCompensationStockBasedCompensationCurrentYearPerShareAverageFairValueandValuationModelAssumptionsDetails</Role>
      <ShortName>Stock-Based Compensation Stock-Based Compensation (Current Year Per Share Average Fair Value and Valuation Model Assumptions) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>9955579 - Disclosure - Stock-Based Compensation (Summary Of SAR Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/StockBasedCompensationSummaryOfSARActivityDetails</Role>
      <ShortName>Stock-Based Compensation (Summary Of SAR Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/StockBasedCompensationTables</ParentRole>
      <Position>94</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>9955580 - Disclosure - Revenue from Contracts with Customers (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/RevenuefromContractswithCustomersNarrativeDetails</Role>
      <ShortName>Revenue from Contracts with Customers (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/RevenuefromContractswithCustomersTables</ParentRole>
      <Position>95</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>9955581 - Disclosure - Revenue from Contracts with Customers (Schedule of Disaggregation of Revenue) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/RevenuefromContractswithCustomersScheduleofDisaggregationofRevenueDetails</Role>
      <ShortName>Revenue from Contracts with Customers (Schedule of Disaggregation of Revenue) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/RevenuefromContractswithCustomersTables</ParentRole>
      <Position>96</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>9955582 - Disclosure - Revenue from Contracts with Customers (Schedule of Contract with Customer, Asset and Liability) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/RevenuefromContractswithCustomersScheduleofContractwithCustomerAssetandLiabilityDetails</Role>
      <ShortName>Revenue from Contracts with Customers (Schedule of Contract with Customer, Asset and Liability) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/RevenuefromContractswithCustomersTables</ParentRole>
      <Position>97</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>9955583 - Disclosure - Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueMeasurementsSummaryOfAssetsAndLiabilitiesMeasuredAtFairValueOnARecurringBasisDetails</Role>
      <ShortName>Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>98</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>9955584 - Disclosure - Fair Value Measurements (Summary Of Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueMeasurementsSummaryOfChangesInLevel3AssetsAndLiabilitiesMeasuredAtFairValueOnARecurringBasisDetails</Role>
      <ShortName>Fair Value Measurements (Summary Of Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>99</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>9955585 - Disclosure - Fair Value Measurements (Summary Of Gains And Losses On Level 3 Assets And Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueMeasurementsSummaryOfGainsAndLossesOnLevel3AssetsAndLiabilitiesDetails</Role>
      <ShortName>Fair Value Measurements (Summary Of Gains And Losses On Level 3 Assets And Liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>100</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>9955586 - Disclosure - Fair Value Measurements (Summary Of Quantitative Information About Level 3 Fair Value Measurements) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueMeasurementsSummaryOfQuantitativeInformationAboutLevel3FairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements (Summary Of Quantitative Information About Level 3 Fair Value Measurements) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>101</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>9955587 - Disclosure - Fair Value Measurements (Schedule of Fair Value Disclosures Measured On Nonrecurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueMeasurementsScheduleofFairValueDisclosuresMeasuredOnNonrecurringBasisDetails</Role>
      <ShortName>Fair Value Measurements (Schedule of Fair Value Disclosures Measured On Nonrecurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>102</Position>
    </Report>
    <Report instance="cbsh-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>9955588 - Disclosure - Fair Value Of Financial Instruments (Schedule Of Estimated Fair Value Of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.commercebank.com/role/FairValueOfFinancialInstrumentsScheduleOfEstimatedFairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Of Financial Instruments (Schedule Of Estimated Fair Value Of Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.commercebank.com/role/FairValueOfFinancialInstrumentsTables</ParentRole>
      <Position>103</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="cbsh-20260331.htm">cbsh-20260331.htm</File>
    <File>cbsh-20260331.xsd</File>
    <File>cbsh-20260331_cal.xml</File>
    <File>cbsh-20260331_def.xml</File>
    <File>cbsh-20260331_lab.xml</File>
    <File>cbsh-20260331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="2635">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="29">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>
