<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>182</ContextCount>
  <ElementCount>270</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>63</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001002 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002003 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1003004 - Statement - Condensed Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/CondensedConsolidatedStatementsofOperations</Role>
      <ShortName>Condensed Consolidated Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004005 - Statement - Condensed Consolidated Statements of Changes in Stockholders' Deficit (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/CondensedConsolidatedStatementsofChangesinStockholdersDeficitUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Changes in Stockholders' Deficit (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1005006 - Statement - Condensed Consolidated Statement of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/CondensedConsolidatedStatementofCashFlows</Role>
      <ShortName>Condensed Consolidated Statement of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>2101101 - Disclosure - ORGANIZATION AND RELATIONSHIPS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/ORGANIZATIONANDRELATIONSHIPS</Role>
      <ShortName>ORGANIZATION AND RELATIONSHIPS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2103102 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2106103 - Disclosure - MERGERS AND ACQUISITIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/MERGERSANDACQUISITIONS</Role>
      <ShortName>MERGERS AND ACQUISITIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2110104 - Disclosure - REFRANCHISING</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/REFRANCHISING</Role>
      <ShortName>REFRANCHISING</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2115105 - Disclosure - NOTES RECEIVABLE</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://fatbrands.com/role/NOTESRECEIVABLE</Role>
      <ShortName>NOTES RECEIVABLE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2117106 - Disclosure - PROPERTY AND EQUIPMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/PROPERTYANDEQUIPMENT</Role>
      <ShortName>PROPERTY AND EQUIPMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2120107 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS, NET</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GOODWILLANDOTHERINTANGIBLEASSETSNET</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS, NET</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2125108 - Disclosure - DEFERRED INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DEFERREDINCOME</Role>
      <ShortName>DEFERRED INCOME</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2128109 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/INCOMETAXES</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2131110 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/LEASES</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2137111 - Disclosure - DEBT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DEBT</Role>
      <ShortName>DEBT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2141112 - Disclosure - SERIES B CUMULATIVE PREFERRED STOCK</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SERIESBCUMULATIVEPREFERREDSTOCK</Role>
      <ShortName>SERIES B CUMULATIVE PREFERRED STOCK</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2143113 - Disclosure - SHARE-BASED COMPENSATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SHAREBASEDCOMPENSATION</Role>
      <ShortName>SHARE-BASED COMPENSATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2145114 - Disclosure - WARRANTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/WARRANTS</Role>
      <ShortName>WARRANTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2149115 - Disclosure - DIVIDENDS ON COMMON STOCK</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DIVIDENDSONCOMMONSTOCK</Role>
      <ShortName>DIVIDENDS ON COMMON STOCK</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2151116 - Disclosure - COMMITMENTS AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/COMMITMENTSANDCONTINGENCIES</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2153117 - Disclosure - GEOGRAPHIC INFORMATION AND MAJOR FRANCHISEES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GEOGRAPHICINFORMATIONANDMAJORFRANCHISEES</Role>
      <ShortName>GEOGRAPHIC INFORMATION AND MAJOR FRANCHISEES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2156118 - Disclosure - SUBSEQUENT EVENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SUBSEQUENTEVENTS</Role>
      <ShortName>SUBSEQUENT EVENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2204201 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - MERGERS AND ACQUISITIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/MERGERSANDACQUISITIONSTables</Role>
      <ShortName>MERGERS AND ACQUISITIONS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/MERGERSANDACQUISITIONS</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2311302 - Disclosure - REFRANCHISING (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/REFRANCHISINGTables</Role>
      <ShortName>REFRANCHISING (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/REFRANCHISING</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2318303 - Disclosure - PROPERTY AND EQUIPMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/PROPERTYANDEQUIPMENTTables</Role>
      <ShortName>PROPERTY AND EQUIPMENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/PROPERTYANDEQUIPMENT</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2321304 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS, NET (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GOODWILLANDOTHERINTANGIBLEASSETSNETTables</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS, NET (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/GOODWILLANDOTHERINTANGIBLEASSETSNET</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2326305 - Disclosure - DEFERRED INCOME (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DEFERREDINCOMETables</Role>
      <ShortName>DEFERRED INCOME (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/DEFERREDINCOME</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2329306 - Disclosure - INCOME TAXES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/INCOMETAXESTables</Role>
      <ShortName>INCOME TAXES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/INCOMETAXES</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2332307 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/LEASESTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/LEASES</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2338308 - Disclosure - DEBT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DEBTTables</Role>
      <ShortName>DEBT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/DEBT</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2346309 - Disclosure - WARRANTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/WARRANTSTables</Role>
      <ShortName>WARRANTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/WARRANTS</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2354310 - Disclosure - GEOGRAPHIC INFORMATION AND MAJOR FRANCHISEES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GEOGRAPHICINFORMATIONANDMAJORFRANCHISEESTables</Role>
      <ShortName>GEOGRAPHIC INFORMATION AND MAJOR FRANCHISEES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://fatbrands.com/role/GEOGRAPHICINFORMATIONANDMAJORFRANCHISEES</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2402401 - Disclosure - ORGANIZATION AND RELATIONSHIPS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/ORGANIZATIONANDRELATIONSHIPSNarrativeDetails</Role>
      <ShortName>ORGANIZATION AND RELATIONSHIPS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESNarrativeDetails</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - MERGERS AND ACQUISITIONS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/MERGERSANDACQUISITIONSNarrativeDetails</Role>
      <ShortName>MERGERS AND ACQUISITIONS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - MERGERS AND ACQUISITIONS - PRO FORMA REVENUE AND NET INCOME (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/MERGERSANDACQUISITIONSPROFORMAREVENUEANDNETINCOMEDetails</Role>
      <ShortName>MERGERS AND ACQUISITIONS - PRO FORMA REVENUE AND NET INCOME (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2412405 - Disclosure - REFRANCHISING - Schedule of Remaining Assets Classified as Held for Sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/REFRANCHISINGScheduleofRemainingAssetsClassifiedasHeldforSaleDetails</Role>
      <ShortName>REFRANCHISING - Schedule of Remaining Assets Classified as Held for Sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2413406 - Disclosure - REFRANCHISING - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/REFRANCHISINGNarrativeDetails</Role>
      <ShortName>REFRANCHISING - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2414407 - Disclosure - REFRANCHISING - Schedule of Gain on Refranchising Restaurant Costs and Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/REFRANCHISINGScheduleofGainonRefranchisingRestaurantCostsandExpensesDetails</Role>
      <ShortName>REFRANCHISING - Schedule of Gain on Refranchising Restaurant Costs and Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2416408 - Disclosure - NOTES RECEIVABLE - Narrative (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://fatbrands.com/role/NOTESRECEIVABLENarrativeDetails</Role>
      <ShortName>NOTES RECEIVABLE - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2419409 - Disclosure - PROPERTY AND EQUIPMENT (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/PROPERTYANDEQUIPMENTDetails</Role>
      <ShortName>PROPERTY AND EQUIPMENT (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://fatbrands.com/role/PROPERTYANDEQUIPMENTTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2422410 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Changes in Carrying Value of Goodwill and Other Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GOODWILLANDOTHERINTANGIBLEASSETSNETChangesinCarryingValueofGoodwillandOtherIntangibleAssetsDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Changes in Carrying Value of Goodwill and Other Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2423411 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Gross Carrying Value and Accumulated Amortization (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GOODWILLANDOTHERINTANGIBLEASSETSNETGrossCarryingValueandAccumulatedAmortizationDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Gross Carrying Value and Accumulated Amortization (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2424412 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Expected Future Amortization (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GOODWILLANDOTHERINTANGIBLEASSETSNETExpectedFutureAmortizationDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Expected Future Amortization (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2427413 - Disclosure - DEFERRED INCOME - Schedule of Deferred Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DEFERREDINCOMEScheduleofDeferredIncomeDetails</Role>
      <ShortName>DEFERRED INCOME - Schedule of Deferred Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2430414 - Disclosure - INCOME TAXES - Schedule for Benefit of Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/INCOMETAXESScheduleforBenefitofIncomeTaxesDetails</Role>
      <ShortName>INCOME TAXES - Schedule for Benefit of Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2433415 - Disclosure - LEASES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/LEASESNarrativeDetails</Role>
      <ShortName>LEASES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2434416 - Disclosure - LEASES - Summary of Operating Lease Right of Use Assets and Operating Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/LEASESSummaryofOperatingLeaseRightofUseAssetsandOperatingLeaseLiabilitiesDetails</Role>
      <ShortName>LEASES - Summary of Operating Lease Right of Use Assets and Operating Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2435417 - Disclosure - LEASES - Schedule of Contractual Future Maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/LEASESScheduleofContractualFutureMaturitiesDetails</Role>
      <ShortName>LEASES - Schedule of Contractual Future Maturities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2436418 - Disclosure - LEASES - Summary of Supplemental Cash Flow Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/LEASESSummaryofSupplementalCashFlowInformationDetails</Role>
      <ShortName>LEASES - Summary of Supplemental Cash Flow Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2439419 - Disclosure - DEBT - Schedule of Securitization of Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://fatbrands.com/role/DEBTScheduleofSecuritizationofNotesDetails</Role>
      <ShortName>DEBT - Schedule of Securitization of Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2440420 - Disclosure - DEBT - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DEBTNarrativeDetails</Role>
      <ShortName>DEBT - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2442421 - Disclosure - SERIES B CUMULATIVE PREFERRED STOCK - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SERIESBCUMULATIVEPREFERREDSTOCKNarrativeDetails</Role>
      <ShortName>SERIES B CUMULATIVE PREFERRED STOCK - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2444422 - Disclosure - SHARE-BASED COMPENSATION - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/SHAREBASEDCOMPENSATIONNarrativeDetails</Role>
      <ShortName>SHARE-BASED COMPENSATION - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2447423 - Disclosure - WARRANTS - Summary of Warrant Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/WARRANTSSummaryofWarrantActivityDetails</Role>
      <ShortName>WARRANTS - Summary of Warrant Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2448424 - Disclosure - WARRANTS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/WARRANTSNarrativeDetails</Role>
      <ShortName>WARRANTS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2450425 - Disclosure - DIVIDENDS ON COMMON STOCK - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/DIVIDENDSONCOMMONSTOCKNarrativeDetails</Role>
      <ShortName>DIVIDENDS ON COMMON STOCK - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2452426 - Disclosure - COMMITMENTS AND CONTINGENCIES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="fat-20220327.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2455427 - Disclosure - GEOGRAPHIC INFORMATION AND MAJOR FRANCHISEEE - Schedule of Revenues by Geographic Area (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://fatbrands.com/role/GEOGRAPHICINFORMATIONANDMAJORFRANCHISEEEScheduleofRevenuesbyGeographicAreaDetails</Role>
      <ShortName>GEOGRAPHIC INFORMATION AND MAJOR FRANCHISEEE - Schedule of Revenues by Geographic Area (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="fat-20220327.htm">fat-20220327.htm</File>
    <File>fat-20220327.xsd</File>
    <File>fat-20220327_cal.xml</File>
    <File>fat-20220327_def.xml</File>
    <File>fat-20220327_lab.xml</File>
    <File>fat-20220327_pre.xml</File>
    <File>fat-20220327x10xqexx311.htm</File>
    <File>fat-20220327x10xqexx312.htm</File>
    <File>fat-20220327x10xqexx321.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>fat-20220327_g1.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="538">http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy items="40">http://xbrl.sec.gov/dei/2021q4</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
