<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>12</ContextCount>
  <ElementCount>78</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>11</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>2</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000001 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://seic.com/20140130/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>020000 - Document - Risk/Return Summary {Unlabeled} - Class A Prospectus - SIMT LARGE CAP GROWTH FUND</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://seic.com/20140130/role/DocumentRiskReturnSummaryUnlabeledClassAProspectusSIMTLARGECAPGROWTHFUND</Role>
      <ShortName>Risk/Return Summary  - Class A Prospectus - SIMT LARGE CAP GROWTH FUND</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>020006 - Disclosure - Risk/Return Detail Data {Elements} - Class A Prospectus - SIMT LARGE CAP GROWTH FUND</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://seic.com/20140130/role/DisclosureRiskReturnDetailDataElementsClassAProspectusSIMTLARGECAPGROWTHFUND</Role>
      <ShortName>Risk/Return Detail Data  - Class A Prospectus - SIMT LARGE CAP GROWTH FUND</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>020007 - Document - Risk/Return Summary {Unlabeled} - Class I Prospectus - SIMT Small Cap Fund</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://seic.com/20140130/role/DocumentRiskReturnSummaryUnlabeledClassIProspectusSIMTSmallCapFund</Role>
      <ShortName>Risk/Return Summary  - Class I Prospectus - SIMT Small Cap Fund</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>020013 - Disclosure - Risk/Return Detail Data {Elements} - Class I Prospectus - SIMT Small Cap Fund</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://seic.com/20140130/role/DisclosureRiskReturnDetailDataElementsClassIProspectusSIMTSmallCapFund</Role>
      <ShortName>Risk/Return Detail Data  - Class I Prospectus - SIMT Small Cap Fund</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.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>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs />
  <InputFiles>
    <File>ck0000804239-20140130.xml</File>
    <File>ck0000804239-20140130.xsd</File>
    <File>ck0000804239-20140130_cal.xml</File>
    <File>ck0000804239-20140130_def.xml</File>
    <File>ck0000804239-20140130_lab.xml</File>
    <File>ck0000804239-20140130_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>BarChart1.jpg</File>
    <File>BarChart2.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
