<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.2.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>6</ContextCount>
  <ElementCount>49</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>5</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>2</UnitCount>
  <MyReports>
    <Report instance="ft-20221121.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000000 - Document - Document and Entity Information {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ftportfolios.com/role/DocumentDocumentandEntityInformationElements</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory></MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="ft-20221121.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>000019 - Disclosure - Risk/Return Detail Data {Elements} - FT Cboe Vest US Equity Buffer ETF - November</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ftportfolios.com/role/DisclosureRiskReturnDetailDataElementsFTCboeVestUSEquityBufferETF-November</Role>
      <ShortName>Risk/Return Detail Data- FT Cboe Vest US Equity Buffer ETF - November</ShortName>
      <MenuCategory></MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="ft-20221121.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>040000 - Disclosure - Risk/Return Detail Data {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/rr/role/RiskReturnDetailData</Role>
      <ShortName>Risk/Return Detail Data</ShortName>
      <MenuCategory></MenuCategory>
      <Position>3</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 3 fact(s) appearing in ix:hidden were eligible for transformation: rr:PortfolioTurnoverRate, rr:ProspectusDate, rr:RiskReturnHeading -  ft-20221121.htm 7, 14, 17</Log>
  </Logs>
  <InputFiles>
    <File doctype="497" original="ft-20221121.htm">ft-20221121.htm</File>
    <File>ft-20221121.xsd</File>
    <File>ft-20221121_cal.xml</File>
    <File>ft-20221121_def.xml</File>
    <File>ft-20221121_lab.xml</File>
    <File>ft-20221121_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>buffer_barchart2021.jpg</File>
    <File>buffer_linechart2021.jpg</File>
    <File>fnov_dgf.jpg</File>
    <File>imge8cf89071.gif</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="8">http://xbrl.sec.gov/dei/2021</BaseTaxonomy>
    <BaseTaxonomy items="47">http://xbrl.sec.gov/rr/2021</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
