<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>398</ContextCount>
  <ElementCount>462</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>121</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0000002 - Document - Audit Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/AuditInformation</Role>
      <ShortName>Audit Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952151 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952152 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CONSOLIDATEDBALANCESHEETSParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952153 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONSANDCOMPREHENSIVEINCOME</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952154 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952155 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952156 - Disclosure - Business Overview and Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPolicies</Role>
      <ShortName>Business Overview and Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952157 - Disclosure - Product Sales</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/ProductSales</Role>
      <ShortName>Product Sales</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952158 - Disclosure - Collaboration, License, and Other Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreements</Role>
      <ShortName>Collaboration, License, and Other Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - Marketable Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/MarketableSecurities</Role>
      <ShortName>Marketable Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Inventories</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/Inventories</Role>
      <ShortName>Inventories</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - Property, Plant, and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/PropertyPlantandEquipment</Role>
      <ShortName>Property, Plant, and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IntangibleAssets</Role>
      <ShortName>Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Accrued Expenses and Other Current Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/AccruedExpensesandOtherCurrentLiabilities</Role>
      <ShortName>Accrued Expenses and Other Current Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Long-Term Incentive Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlans</Role>
      <ShortName>Long-Term Incentive Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - Employee Savings Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/EmployeeSavingsPlans</Role>
      <ShortName>Employee Savings Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9952171 - Disclosure - Legal Matters</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LegalMatters</Role>
      <ShortName>Legal Matters</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9952172 - Disclosure - Net Income Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/NetIncomePerShare</Role>
      <ShortName>Net Income Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9952173 - Disclosure - Statement of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StatementofCashFlows</Role>
      <ShortName>Statement of Cash Flows</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.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>27</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995447 - Disclosure - Insider Trading Policies and Procedures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc</Role>
      <ShortName>Insider Trading Policies and Procedures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure</Role>
      <ShortName>Cybersecurity Risk Management and Strategy Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - Business Overview and Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Business Overview and Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPolicies</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - Business Overview and Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPoliciesTables</Role>
      <ShortName>Business Overview and Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPolicies</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - Product Sales (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/ProductSalesTables</Role>
      <ShortName>Product Sales (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/ProductSales</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - Collaboration, License, and Other Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsTables</Role>
      <ShortName>Collaboration, License, and Other Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreements</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - Marketable Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/MarketableSecuritiesTables</Role>
      <ShortName>Marketable Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/MarketableSecurities</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/FairValueMeasurements</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - Inventories (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/InventoriesTables</Role>
      <ShortName>Inventories (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/Inventories</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - Property, Plant, and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/PropertyPlantandEquipmentTables</Role>
      <ShortName>Property, Plant, and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/PropertyPlantandEquipment</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IntangibleAssetsTables</Role>
      <ShortName>Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/IntangibleAssets</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - Accrued Expenses and Other Current Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/AccruedExpensesandOtherCurrentLiabilitiesTables</Role>
      <ShortName>Accrued Expenses and Other Current Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/AccruedExpensesandOtherCurrentLiabilities</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/Debt</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/Leases</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - Stockholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StockholdersEquityTables</Role>
      <ShortName>Stockholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/StockholdersEquity</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - Long-Term Incentive Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlansTables</Role>
      <ShortName>Long-Term Incentive Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/LongTermIncentivePlans</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/IncomeTaxes</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - Net Income Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/NetIncomePerShareTables</Role>
      <ShortName>Net Income Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/NetIncomePerShare</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - Statement of Cash Flows (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StatementofCashFlowsTables</Role>
      <ShortName>Statement of Cash Flows (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/StatementofCashFlows</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - Business Overview and Summary of Significant Accounting Policies - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Business Overview and Summary of Significant Accounting Policies - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPoliciesTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - Business Overview and Summary of Significant Accounting Policies - Schedule of Significant Segment Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPoliciesScheduleofSignificantSegmentExpensesDetails</Role>
      <ShortName>Business Overview and Summary of Significant Accounting Policies - Schedule of Significant Segment Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - Business Overview and Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/BusinessOverviewandSummaryofSignificantAccountingPoliciesScheduleofEstimatedUsefulLivesDetails</Role>
      <ShortName>Business Overview and Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - Product Sales - Schedule of Net Product Sales (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/ProductSalesScheduleofNetProductSalesDetails</Role>
      <ShortName>Product Sales - Schedule of Net Product Sales (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - Product Sales - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/ProductSalesNarrativeDetails</Role>
      <ShortName>Product Sales - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - Product Sales - Schedule of Concentration of Risk, by Risk Factor (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/ProductSalesScheduleofConcentrationofRiskbyRiskFactorDetails</Role>
      <ShortName>Product Sales - Schedule of Concentration of Risk, by Risk Factor (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - Product Sales - Schedule of Sales Related Deductions Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/ProductSalesScheduleofSalesRelatedDeductionsActivityDetails</Role>
      <ShortName>Product Sales - Schedule of Sales Related Deductions Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Sanofi (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsScheduleofCollaborationRevenueEarnedFromSanofiDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Sanofi (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - Collaboration, License, and Other Agreements - Sanofi, Antibody Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsSanofiAntibodyNarrativeDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Sanofi, Antibody Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - Collaboration, License, and Other Agreements - Schedule of Accounts Receivable and Deferred Revenue Information, Antibody Collaboration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsScheduleofAccountsReceivableandDeferredRevenueInformationAntibodyCollaborationDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Schedule of Accounts Receivable and Deferred Revenue Information, Antibody Collaboration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - Collaboration, License, and Other Agreements - Sanofi, Immuno-Oncology Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsSanofiImmunoOncologyNarrativeDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Sanofi, Immuno-Oncology Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - Collaboration, License, and Other Agreements - Bayer Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsBayerNarrativeDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Bayer Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Bayer (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsScheduleofCollaborationRevenueEarnedFromBayerDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Bayer (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - Collaboration, License, and Other Agreements - Schedule of Contract Balances, Bayer Collaborative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsScheduleofContractBalancesBayerCollaborativeDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Schedule of Contract Balances, Bayer Collaborative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Roche (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsAmountsRecognizedinStatementofOperationswithRocheDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Roche (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - Collaboration, License, and Other Agreements - Other Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/CollaborationLicenseandOtherAgreementsOtherNarrativeDetails</Role>
      <ShortName>Collaboration, License, and Other Agreements - Other Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - Marketable Securities - Schedule of Investments in Available For Sale Debt Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/MarketableSecuritiesScheduleofInvestmentsinAvailableForSaleDebtSecuritiesDetails</Role>
      <ShortName>Marketable Securities - Schedule of Investments in Available For Sale Debt Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - Marketable Securities - Schedule of Debt Securities Based on Contractual Maturity Dates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/MarketableSecuritiesScheduleofDebtSecuritiesBasedonContractualMaturityDatesDetails</Role>
      <ShortName>Marketable Securities - Schedule of Debt Securities Based on Contractual Maturity Dates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - Marketable Securities - Schedule of Fair Value and Unrealized Losses of Debt Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/MarketableSecuritiesScheduleofFairValueandUnrealizedLossesofDebtSecuritiesDetails</Role>
      <ShortName>Marketable Securities - Schedule of Fair Value and Unrealized Losses of Debt Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - Marketable Securities - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/MarketableSecuritiesNarrativeDetails</Role>
      <ShortName>Marketable Securities - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/FairValueMeasurementsScheduleofAssetsMeasuredatFairValueonaRecurringBasisDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - Fair Value Measurements - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/FairValueMeasurementsNarrativeDetails</Role>
      <ShortName>Fair Value Measurements - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - Inventories - Schedule of Inventories (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/InventoriesScheduleofInventoriesDetails</Role>
      <ShortName>Inventories - Schedule of Inventories (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - Inventories - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/InventoriesNarrativeDetails</Role>
      <ShortName>Inventories - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - Property, Plant, and Equipment - Schedule of Property, Plant, and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentDetails</Role>
      <ShortName>Property, Plant, and Equipment - Schedule of Property, Plant, and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - Property, Plant, and Equipment - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/PropertyPlantandEquipmentNarrativeDetails</Role>
      <ShortName>Property, Plant, and Equipment - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - Intangible Assets - Schedule of Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IntangibleAssetsScheduleofIntangibleAssetsDetails</Role>
      <ShortName>Intangible Assets - Schedule of Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - Intangible Assets - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IntangibleAssetsNarrativeDetails</Role>
      <ShortName>Intangible Assets - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/AccruedExpensesandOtherCurrentLiabilitiesScheduleofAccruedExpensesandOtherCurrentLiabilitiesDetails</Role>
      <ShortName>Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - Debt - Summary of Issued Senior Unsecured Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.regeneron.com/role/DebtSummaryofIssuedSeniorUnsecuredNotesDetails</Role>
      <ShortName>Debt - Summary of Issued Senior Unsecured Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - Debt - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/DebtNarrativeDetails</Role>
      <ShortName>Debt - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - Leases - Leases Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LeasesLeasesNarrativeDetails</Role>
      <ShortName>Leases - Leases Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - Leases - Amounts recognized in Condensed Consolidated Balance Sheet (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LeasesAmountsrecognizedinCondensedConsolidatedBalanceSheetDetails</Role>
      <ShortName>Leases - Amounts recognized in Condensed Consolidated Balance Sheet (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - Leases - Finance lease costs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LeasesFinanceleasecostsDetails</Role>
      <ShortName>Leases - Finance lease costs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - Leases - Other information related to finance lease (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LeasesOtherinformationrelatedtofinanceleaseDetails</Role>
      <ShortName>Leases - Other information related to finance lease (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - Leases - Supplemental cash flows (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LeasesSupplementalcashflowsDetails</Role>
      <ShortName>Leases - Supplemental cash flows (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9955564 - Disclosure - Leases - Analysis of lease liability maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LeasesAnalysisofleaseliabilitymaturitiesDetails</Role>
      <ShortName>Leases - Analysis of lease liability maturities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9955565 - Disclosure - Stockholders' Equity - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StockholdersEquityNarrativeDetails</Role>
      <ShortName>Stockholders' Equity - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9955566 - Disclosure - Stockholders' Equity - Schedule of Repurchased Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StockholdersEquityScheduleofRepurchasedSharesDetails</Role>
      <ShortName>Stockholders' Equity - Schedule of Repurchased Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9955567 - Disclosure - Long-Term Incentive Plans - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlansNarrativeDetails</Role>
      <ShortName>Long-Term Incentive Plans - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9955568 - Disclosure - Long-Term Incentive Plans - Summary of transactions involving stock option awards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlansSummaryoftransactionsinvolvingstockoptionawardsDetails</Role>
      <ShortName>Long-Term Incentive Plans - Summary of transactions involving stock option awards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9955569 - Disclosure - Long-Term Incentive Plans - Summary of weighted-average exercise prices and weighted-average grant-date fair values of options issued (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlansSummaryofweightedaverageexercisepricesandweightedaveragegrantdatefairvaluesofoptionsissuedDetails</Role>
      <ShortName>Long-Term Incentive Plans - Summary of weighted-average exercise prices and weighted-average grant-date fair values of options issued (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>9955570 - Disclosure - Long-Term Incentive Plans - Summary of weighted-average values of assumptions used in computing fair value of option grants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlansSummaryofweightedaveragevaluesofassumptionsusedincomputingfairvalueofoptiongrantsDetails</Role>
      <ShortName>Long-Term Incentive Plans - Summary of weighted-average values of assumptions used in computing fair value of option grants (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>9955571 - Disclosure - Long-Term Incentive Plans - Summary of activity related to restricted stock awards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlansSummaryofactivityrelatedtorestrictedstockawardsDetails</Role>
      <ShortName>Long-Term Incentive Plans - Summary of activity related to restricted stock awards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>9955572 - Disclosure - Long-Term Incentive Plans - Summary of weighted-average values of assumptions used in computing fair value of performance-based options (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LongTermIncentivePlansSummaryofweightedaveragevaluesofassumptionsusedincomputingfairvalueofperformancebasedoptionsDetails</Role>
      <ShortName>Long-Term Incentive Plans - Summary of weighted-average values of assumptions used in computing fair value of performance-based options (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>9955573 - Disclosure - Employee Savings Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/EmployeeSavingsPlansDetails</Role>
      <ShortName>Employee Savings Plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/EmployeeSavingsPlans</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>9955574 - Disclosure - Income Taxes - Schedule of income before income tax (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxesScheduleofincomebeforeincometaxDetails</Role>
      <ShortName>Income Taxes - Schedule of income before income tax (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>9955575 - Disclosure - Income Taxes - Schedule of components of income tax expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxesScheduleofcomponentsofincometaxexpenseDetails</Role>
      <ShortName>Income Taxes - Schedule of components of income tax expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>9955576 - Disclosure - Income Taxes - Schedule of effective income tax rate reconciliation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxesScheduleofeffectiveincometaxratereconciliationDetails</Role>
      <ShortName>Income Taxes - Schedule of effective income tax rate reconciliation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>9955577 - Disclosure - Income Taxes - Schedule of deferred tax assets and liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxesScheduleofdeferredtaxassetsandliabilitiesDetails</Role>
      <ShortName>Income Taxes - Schedule of deferred tax assets and liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>9955578 - Disclosure - Income Taxes - Schedule of unrecognized tax benefits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxesScheduleofunrecognizedtaxbenefitsDetails</Role>
      <ShortName>Income Taxes - Schedule of unrecognized tax benefits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>9955579 - Disclosure - Income Taxes - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/IncomeTaxesNarrativeDetails</Role>
      <ShortName>Income Taxes - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>9955580 - Disclosure - Legal Matters (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/LegalMattersDetails</Role>
      <ShortName>Legal Matters (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.regeneron.com/role/LegalMatters</ParentRole>
      <Position>99</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>9955581 - Disclosure - Net Income Per Share - Schedule of Basic and Diluted Net Income Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/NetIncomePerShareScheduleofBasicandDilutedNetIncomePerShareDetails</Role>
      <ShortName>Net Income Per Share - Schedule of Basic and Diluted Net Income Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>9955582 - Disclosure - Net Income Per Share - Schedule of Antidilutive Securities Excluded From Computation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/NetIncomePerShareScheduleofAntidilutiveSecuritiesExcludedFromComputationDetails</Role>
      <ShortName>Net Income Per Share - Schedule of Antidilutive Securities Excluded From Computation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>9955583 - Disclosure - Statement of Cash Flows - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StatementofCashFlowsScheduleofReconciliationofCashCashEquivalentsandRestrictedCashDetails</Role>
      <ShortName>Statement of Cash Flows - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="regn-20241231.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>9955584 - Disclosure - Statement of Cash Flows - Summary of Non-Cash Investing and Financing Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regeneron.com/role/StatementofCashFlowsSummaryofNonCashInvestingandFinancingActivitiesDetails</Role>
      <ShortName>Statement of Cash Flows - Summary of Non-Cash Investing and Financing Activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <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-K" isDefinitelyFs="true" isUsgaap="true" original="regn-20241231.htm">regn-20241231.htm</File>
    <File>regn-20241231.xsd</File>
    <File>regn-20241231_cal.xml</File>
    <File>regn-20241231_def.xml</File>
    <File>regn-20241231_lab.xml</File>
    <File>regn-20241231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>regn-20241231_g1.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="4">http://fasb.org/srt/2024</BaseTaxonomy>
    <BaseTaxonomy items="1209">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="15">http://xbrl.sec.gov/cyd/2024</BaseTaxonomy>
    <BaseTaxonomy items="39">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="12">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
