<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.4</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>393</ContextCount>
  <ElementCount>606</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>122</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-document-and-entity-information</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-consolidated-balance-sheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Consolidated Balance Sheets (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-consolidated-balance-sheets-parentheticals</Role>
      <ShortName>Consolidated Balance Sheets (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-consolidated-statements-of-comprehensive-income-</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-consolidated-statements-of-stockholders-equity</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Consolidated Statements of Stockholders' Equity (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-consolidated-statements-of-stockholders-equity-parentheticals</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-consolidated-statements-of-cash-flows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>995443 - Disclosure - Award Timing Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/AwardTimingDisclosure</Role>
      <ShortName>Award Timing Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.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>9</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.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>10</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.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>11</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995551 - Disclosure - Note 1 - Description of Business</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-1-description-of-business</Role>
      <ShortName>Note 1 - Description of Business</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995552 - Disclosure - Note 2 - Summary of Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies</Role>
      <ShortName>Note 2 - Summary of Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995553 - Disclosure - Note 3 - Acquisitions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-3-acquisitions</Role>
      <ShortName>Note 3 - Acquisitions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995554 - Disclosure - Note 4 - Redeemable Noncontrolling Interests</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-4-redeemable-noncontrolling-interests</Role>
      <ShortName>Note 4 - Redeemable Noncontrolling Interests</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995555 - Disclosure - Note 5 - Derivative Instruments and Hedging Activities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-5-derivative-instruments-and-hedging-activities</Role>
      <ShortName>Note 5 - Derivative Instruments and Hedging Activities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995556 - Disclosure - Note 6 - Accumulated Other Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-6-accumulated-other-comprehensive-income-loss</Role>
      <ShortName>Note 6 - Accumulated Other Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995557 - Disclosure - Note 7 - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-7-segment-reporting</Role>
      <ShortName>Note 7 - Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995558 - Disclosure - Note 8 - Balance Sheet Details</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details</Role>
      <ShortName>Note 8 - Balance Sheet Details</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995559 - Disclosure - Note 9 - Goodwill and Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-9-goodwill-and-intangible-assets</Role>
      <ShortName>Note 9 - Goodwill and Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995560 - Disclosure - Note 10 - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-</Role>
      <ShortName>Note 10 - Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995561 - Disclosure - Note 11 - Product Warranty Obligations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations</Role>
      <ShortName>Note 11 - Product Warranty Obligations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995562 - Disclosure - Note 12 - Credit Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-12-credit-agreements</Role>
      <ShortName>Note 12 - Credit Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995563 - Disclosure - Note 13 - Stock Repurchase Program</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-13-stock-repurchase-program</Role>
      <ShortName>Note 13 - Stock Repurchase Program</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995564 - Disclosure - Note 14 - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-14-earnings-per-share</Role>
      <ShortName>Note 14 - Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995565 - Disclosure - Note 15 - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes</Role>
      <ShortName>Note 15 - Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995566 - Disclosure - Note 16 - Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-16-benefit-plans</Role>
      <ShortName>Note 16 - Benefit Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995567 - Disclosure - Note 17 - Share Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-17-share-plans</Role>
      <ShortName>Note 17 - Share Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995568 - Disclosure - Note 18 - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-18-commitments-and-contingencies</Role>
      <ShortName>Note 18 - Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995569 - Disclosure - Note 19 - Valuation and Qualifying Accounts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-19-valuation-and-qualifying-accounts</Role>
      <ShortName>Note 19 - Valuation and Qualifying Accounts</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995570 - Disclosure - Note 20 - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-20-subsequent-events</Role>
      <ShortName>Note 20 - Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995574 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-significant-accounting-policies-policies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995575 - Disclosure - Note 2 - Summary of Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-tables</Role>
      <ShortName>Note 2 - Summary of Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995576 - Disclosure - Note 3 - Acquisitions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-3-acquisitions-tables</Role>
      <ShortName>Note 3 - Acquisitions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-3-acquisitions</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995577 - Disclosure - Note 4 - Redeemable Noncontrolling Interests (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-4-redeemable-noncontrolling-interests-tables</Role>
      <ShortName>Note 4 - Redeemable Noncontrolling Interests (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-4-redeemable-noncontrolling-interests</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995578 - Disclosure - Note 5 - Derivative Instruments and Hedging Activities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-5-derivative-instruments-and-hedging-activities-tables</Role>
      <ShortName>Note 5 - Derivative Instruments and Hedging Activities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-5-derivative-instruments-and-hedging-activities</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995579 - Disclosure - Note 6 - Accumulated Other Comprehensive Income (Loss) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-6-accumulated-other-comprehensive-income-loss-tables</Role>
      <ShortName>Note 6 - Accumulated Other Comprehensive Income (Loss) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-6-accumulated-other-comprehensive-income-loss</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995580 - Disclosure - Note 7 - Segment Reporting (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-7-segment-reporting-tables</Role>
      <ShortName>Note 7 - Segment Reporting (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-7-segment-reporting</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995581 - Disclosure - Note 8 - Balance Sheet Details (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details-tables</Role>
      <ShortName>Note 8 - Balance Sheet Details (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995582 - Disclosure - Note 9 - Goodwill and Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-9-goodwill-and-intangible-assets-tables</Role>
      <ShortName>Note 9 - Goodwill and Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-9-goodwill-and-intangible-assets</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995583 - Disclosure - Note 10 - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-tables</Role>
      <ShortName>Note 10 - Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-10-leases-</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995584 - Disclosure - Note 11 - Product Warranty Obligations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-tables</Role>
      <ShortName>Note 11 - Product Warranty Obligations (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995585 - Disclosure - Note 12 - Credit Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-12-credit-agreements-tables</Role>
      <ShortName>Note 12 - Credit Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-12-credit-agreements</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995586 - Disclosure - Note 14 - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-14-earnings-per-share-tables</Role>
      <ShortName>Note 14 - Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-14-earnings-per-share</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995587 - Disclosure - Note 15 - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes-tables</Role>
      <ShortName>Note 15 - Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-15-income-taxes</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995588 - Disclosure - Note 17 - Share Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-17-share-plans-tables</Role>
      <ShortName>Note 17 - Share Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-17-share-plans</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>995589 - Disclosure - Note 19 - Valuation and Qualifying Accounts (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-19-valuation-and-qualifying-accounts-tables</Role>
      <ShortName>Note 19 - Valuation and Qualifying Accounts (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-19-valuation-and-qualifying-accounts</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>995590 - Disclosure - Note 2 - Summary of Accounting Policies 1 (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-1-details-textual</Role>
      <ShortName>Note 2 - Summary of Accounting Policies 1 (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-tables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>995591 - Disclosure - Note 2 - Summary of Accounting Policies 2 (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-2-details-textual</Role>
      <ShortName>Note 2 - Summary of Accounting Policies 2 (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-tables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>995592 - Disclosure - Note 2 - Summary of Accounting Policies - Property and Equipment Estimated Useful Lives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-property-and-equipment-estimated-useful-lives-details</Role>
      <ShortName>Note 2 - Summary of Accounting Policies - Property and Equipment Estimated Useful Lives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>995593 - Disclosure - Note 2 - Summary of Accounting Policies - Schedule of Short and Long-term Contract Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-schedule-of-short-and-longterm-contract-liabilities-details</Role>
      <ShortName>Note 2 - Summary of Accounting Policies - Schedule of Short and Long-term Contract Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>995594 - Disclosure - Note 2 - Summary of Accounting Policies - Reconciliation of Contingent Consideration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-2-summary-of-accounting-policies-reconciliation-of-contingent-consideration-details</Role>
      <ShortName>Note 2 - Summary of Accounting Policies - Reconciliation of Contingent Consideration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>995595 - Disclosure - Note 3 - Acquisitions (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-3-acquisitions-details-textual</Role>
      <ShortName>Note 3 - Acquisitions (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-3-acquisitions-tables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>995596 - Disclosure - Note 3 - Acquisitions - Preliminary Price Allocation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-3-acquisitions-preliminary-price-allocation-details</Role>
      <ShortName>Note 3 - Acquisitions - Preliminary Price Allocation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>995597 - Disclosure - Note 4 - Redeemable Noncontrolling Interests (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-4-redeemable-noncontrolling-interests-details-textual</Role>
      <ShortName>Note 4 - Redeemable Noncontrolling Interests (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-4-redeemable-noncontrolling-interests-tables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>995598 - Disclosure - Note 4 - Redeemable Noncontrolling Interests - Redeemable Noncontrolling Interests (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-4-redeemable-noncontrolling-interests-redeemable-noncontrolling-interests-details</Role>
      <ShortName>Note 4 - Redeemable Noncontrolling Interests - Redeemable Noncontrolling Interests (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>995599 - Disclosure - Note 5 - Derivative Instruments and Hedging Activities (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-5-derivative-instruments-and-hedging-activities-details-textual</Role>
      <ShortName>Note 5 - Derivative Instruments and Hedging Activities (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-5-derivative-instruments-and-hedging-activities-tables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>995600 - Disclosure - Note 5 - Derivative Instruments and Hedging Activities - Fair Value of Derivatives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-5-derivative-instruments-and-hedging-activities-fair-value-of-derivatives-details</Role>
      <ShortName>Note 5 - Derivative Instruments and Hedging Activities - Fair Value of Derivatives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>995601 - Disclosure - Note 6 - Accumulated Other Comprehensive Income (Loss) (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-6-accumulated-other-comprehensive-income-loss-details-textual</Role>
      <ShortName>Note 6 - Accumulated Other Comprehensive Income (Loss) (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-6-accumulated-other-comprehensive-income-loss-tables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>995602 - Disclosure - Note 6 - Accumulated Other Comprehensive Loss - Disclosure of Changes in Accumulated Other Comprehensive Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-6-accumulated-other-comprehensive-loss-disclosure-of-changes-in-accumulated-other-comprehensive-loss-details</Role>
      <ShortName>Note 6 - Accumulated Other Comprehensive Loss - Disclosure of Changes in Accumulated Other Comprehensive Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>995603 - Disclosure - Note 7 - Segment Reporting (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-7-segment-reporting-details-textual</Role>
      <ShortName>Note 7 - Segment Reporting (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-7-segment-reporting-tables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>995604 - Disclosure - Note 7 - Segment Reporting - Net Sales by Products and Services (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-7-segment-reporting-net-sales-by-products-and-services-details</Role>
      <ShortName>Note 7 - Segment Reporting - Net Sales by Products and Services (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>995605 - Disclosure - Note 7 - Segment Reporting - Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-7-segment-reporting-segment-information-details</Role>
      <ShortName>Note 7 - Segment Reporting - Segment Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>995606 - Disclosure - Note 8 - Balance Sheet Details (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details-details-textual</Role>
      <ShortName>Note 8 - Balance Sheet Details (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details-tables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>995607 - Disclosure - Note 8 - Balance Sheet Details - Inventories (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details-inventories-details</Role>
      <ShortName>Note 8 - Balance Sheet Details - Inventories (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>995608 - Disclosure - Note 8 - Balance Sheet Details - Property and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details-property-and-equipment-details</Role>
      <ShortName>Note 8 - Balance Sheet Details - Property and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>995609 - Disclosure - Note 8 - Balance Sheet Details - Other Accrued Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-8-balance-sheet-details-other-accrued-liabilities-details</Role>
      <ShortName>Note 8 - Balance Sheet Details - Other Accrued Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>995610 - Disclosure - Note 9 - Goodwill and Intangible Assets (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-9-goodwill-and-intangible-assets-details-textual</Role>
      <ShortName>Note 9 - Goodwill and Intangible Assets (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-9-goodwill-and-intangible-assets-tables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>995611 - Disclosure - Note 9 - Goodwill and Intangible Assets - Carrying Amount of Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-9-goodwill-and-intangible-assets-carrying-amount-of-goodwill-details</Role>
      <ShortName>Note 9 - Goodwill and Intangible Assets - Carrying Amount of Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>995612 - Disclosure - Note 9 - Goodwill and Intangible Assets - Summary of Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-9-goodwill-and-intangible-assets-summary-of-intangible-assets-details</Role>
      <ShortName>Note 9 - Goodwill and Intangible Assets - Summary of Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>995613 - Disclosure - Note 10 - Leases (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-details-textual</Role>
      <ShortName>Note 10 - Leases (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-10-leases-tables</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>995614 - Disclosure - Note 10 - Leases - Leases Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-leases-cost-details</Role>
      <ShortName>Note 10 - Leases - Leases Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>995615 - Disclosure - Note 10 - Leases - Supplement Balance Sheet Information Related to Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-supplement-balance-sheet-information-related-to-leases-details</Role>
      <ShortName>Note 10 - Leases - Supplement Balance Sheet Information Related to Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>995616 - Disclosure - Note 10 - Leases - Supplement Balance Sheet Information Related to Leases (Details) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-supplement-balance-sheet-information-related-to-leases-details-parentheticals</Role>
      <ShortName>Note 10 - Leases - Supplement Balance Sheet Information Related to Leases (Details) (Parentheticals)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>995617 - Disclosure - Note 10 - Leases - Supplement Cash Flow Information Related to Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-supplement-cash-flow-information-related-to-leases-details</Role>
      <ShortName>Note 10 - Leases - Supplement Cash Flow Information Related to Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>995618 - Disclosure - Note 10 - Leases - Weighted Average Remaining Lease Term and Discount Rate Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-weighted-average-remaining-lease-term-and-discount-rate-information-details</Role>
      <ShortName>Note 10 - Leases - Weighted Average Remaining Lease Term and Discount Rate Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>995619 - Disclosure - Note 10 - Leases - Maturities of Lease liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-10-leases-maturities-of-lease-liabilities-details</Role>
      <ShortName>Note 10 - Leases - Maturities of Lease liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>995620 - Disclosure - Note 11 - Product Warranty Obligations (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-details-textual</Role>
      <ShortName>Note 11 - Product Warranty Obligations (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-tables</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>995621 - Disclosure - Note 11 - Product Warranty Obligations - Reconciliation of Product Warranty Liability (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-reconciliation-of-product-warranty-liability-details</Role>
      <ShortName>Note 11 - Product Warranty Obligations - Reconciliation of Product Warranty Liability (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>995622 - Disclosure - Note 11 - Product Warranty Obligations - Recognition of Deferred Revenue Related to Extended Warranties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-recognition-of-deferred-revenue-related-to-extended-warranties-details</Role>
      <ShortName>Note 11 - Product Warranty Obligations - Recognition of Deferred Revenue Related to Extended Warranties (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>995623 - Disclosure - Note 11 - Product Warranty Obligations - Recognition of Deferred Revenue Related to Extended Warranties 2 (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-recognition-of-deferred-revenue-related-to-extended-warranties-2-details</Role>
      <ShortName>Note 11 - Product Warranty Obligations - Recognition of Deferred Revenue Related to Extended Warranties 2 (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>995624 - Disclosure - Note 11 - Product Warranty Obligations - Recognition of Deferred Revenue Related to Extended Warranties (Details) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-recognition-of-deferred-revenue-related-to-extended-warranties-details-parentheticals</Role>
      <ShortName>Note 11 - Product Warranty Obligations - Recognition of Deferred Revenue Related to Extended Warranties (Details) (Parentheticals)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>995625 - Disclosure - Note 11 - Product Warranty Obligations - Deferred Product Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-11-product-warranty-obligations-deferred-product-obligations-details</Role>
      <ShortName>Note 11 - Product Warranty Obligations - Deferred Product Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>995626 - Disclosure - Note 12 - Credit Agreements (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-12-credit-agreements-details-textual</Role>
      <ShortName>Note 12 - Credit Agreements (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-12-credit-agreements-tables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>995627 - Disclosure - Note 12 - Credit Agreements - Long-term Borrowings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-12-credit-agreements-longterm-borrowings-details</Role>
      <ShortName>Note 12 - Credit Agreements - Long-term Borrowings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>995628 - Disclosure - Note 12 - Credit Agreements - Long-term Borrowings (Details) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-12-credit-agreements-longterm-borrowings-details-parentheticals</Role>
      <ShortName>Note 12 - Credit Agreements - Long-term Borrowings (Details) (Parentheticals)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>995629 - Disclosure - Note 12 - Credit Agreements - Maturities of Long-term Borrowings Outstanding (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-12-credit-agreements-maturities-of-longterm-borrowings-outstanding-details</Role>
      <ShortName>Note 12 - Credit Agreements - Maturities of Long-term Borrowings Outstanding (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>995630 - Disclosure - Note 13 - Stock Repurchase Program (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-13-stock-repurchase-program-details-textual</Role>
      <ShortName>Note 13 - Stock Repurchase Program (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-13-stock-repurchase-program</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>995631 - Disclosure - Note 14 - Earnings Per Share (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-14-earnings-per-share-details-textual</Role>
      <ShortName>Note 14 - Earnings Per Share (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-14-earnings-per-share-tables</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>995632 - Disclosure - Note 14 - Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-14-earnings-per-share-reconciliation-of-basic-and-diluted-earnings-per-share-details</Role>
      <ShortName>Note 14 - Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>995633 - Disclosure - Note 15 - Income Taxes (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes-details-textual</Role>
      <ShortName>Note 15 - Income Taxes (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-15-income-taxes-tables</ParentRole>
      <Position>91</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>995634 - Disclosure - Note 15 - Income Taxes - Provision for Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes-provision-for-income-taxes-details</Role>
      <ShortName>Note 15 - Income Taxes - Provision for Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>995635 - Disclosure - Note 15 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes-components-of-deferred-tax-assets-and-liabilities-details</Role>
      <ShortName>Note 15 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>995636 - Disclosure - Note 15 - Income Taxes - Unrecognized Tax Benefits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes-unrecognized-tax-benefits-details</Role>
      <ShortName>Note 15 - Income Taxes - Unrecognized Tax Benefits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>995637 - Disclosure - Note 15 - Income Taxes - Reconciliation of Statutory and Effective Tax Rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes-reconciliation-of-statutory-and-effective-tax-rates-details</Role>
      <ShortName>Note 15 - Income Taxes - Reconciliation of Statutory and Effective Tax Rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>995638 - Disclosure - Note 15 - Income Taxes - Taxes Paid (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-15-income-taxes-taxes-paid-details</Role>
      <ShortName>Note 15 - Income Taxes - Taxes Paid (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>995639 - Disclosure - Note 16 - Benefit Plans (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-16-benefit-plans-details-textual</Role>
      <ShortName>Note 16 - Benefit Plans (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-16-benefit-plans</ParentRole>
      <Position>97</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>995640 - Disclosure - Note 17 - Share Plans (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-17-share-plans-details-textual</Role>
      <ShortName>Note 17 - Share Plans (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-17-share-plans-tables</ParentRole>
      <Position>98</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>995641 - Disclosure - Note 17 - Share Plans - Weighted-average Assumptions used in the Black-Scholes-Merton Option Pricing Model (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-17-share-plans-weightedaverage-assumptions-used-in-the-blackscholesmerton-option-pricing-model-details</Role>
      <ShortName>Note 17 - Share Plans - Weighted-average Assumptions used in the Black-Scholes-Merton Option Pricing Model (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>995642 - Disclosure - Note 17 - Share Plans - Summary of Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-17-share-plans-summary-of-stock-option-activity-details</Role>
      <ShortName>Note 17 - Share Plans - Summary of Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>995643 - Disclosure - Note 17 - Share Plans - Summary of Restricted Share Awards Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-17-share-plans-summary-of-restricted-share-awards-activity-details</Role>
      <ShortName>Note 17 - Share Plans - Summary of Restricted Share Awards Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>995644 - Disclosure - Note 18 - Commitments and Contingencies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-18-commitments-and-contingencies-details-textual</Role>
      <ShortName>Note 18 - Commitments and Contingencies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-18-commitments-and-contingencies</ParentRole>
      <Position>102</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>995645 - Disclosure - Note 19 - Valuation and Qualifying Accounts - Schedule of Valuation and Qualifying Accounts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-19-valuation-and-qualifying-accounts-schedule-of-valuation-and-qualifying-accounts-details</Role>
      <ShortName>Note 19 - Valuation and Qualifying Accounts - Schedule of Valuation and Qualifying Accounts (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="gnrc20251231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>995646 - Disclosure - Note 20 - Subsequent Events (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.generac.com/20251231/role/statement-note-20-subsequent-events-details-textual</Role>
      <ShortName>Note 20 - Subsequent Events (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.generac.com/20251231/role/statement-note-20-subsequent-events</ParentRole>
      <Position>104</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>gnrc-20251231.xsd</File>
    <File>gnrc-20251231_cal.xml</File>
    <File>gnrc-20251231_def.xml</File>
    <File>gnrc-20251231_lab.xml</File>
    <File>gnrc-20251231_pre.xml</File>
    <File doctype="10-K" isDefinitelyFs="true" isUsgaap="true" original="gnrc20251231_10k.htm">gnrc20251231_10k.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>stockgraph.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="5">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="1645">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="12">http://xbrl.sec.gov/cyd/2025</BaseTaxonomy>
    <BaseTaxonomy items="37">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="12">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
