<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Version>2.4.0.6</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>166</ContextCount>
  <ElementCount>80</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>157</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>2</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>001001 - Document - Document And Entity Information {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/DocumentDocumentandEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>011002 - Document - Risk/Return Summary {Unlabeled} (Asset Allocation Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007655Member</Role>
      <ShortName>Risk/Return Summary  (Asset Allocation Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.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>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>061008 - Document - Risk/Return Summary {Unlabeled} (Balanced Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007666Member</Role>
      <ShortName>Risk/Return Summary  (Balanced Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>061013 - Disclosure - Risk/Return Detail Data {Elements} (Balanced Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007666Member</Role>
      <ShortName>Risk/Return Detail Data  (Balanced Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>061014 - Document - Risk/Return Summary {Unlabeled} (Bond &amp; Mortgage Securities Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007677Member</Role>
      <ShortName>Risk/Return Summary  (Bond &amp; Mortgage Securities Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>061019 - Disclosure - Risk/Return Detail Data {Elements} (Bond &amp; Mortgage Securities Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007677Member</Role>
      <ShortName>Risk/Return Detail Data  (Bond &amp; Mortgage Securities Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>061020 - Document - Risk/Return Summary {Unlabeled} (Bond Market Index Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000036925Member</Role>
      <ShortName>Risk/Return Summary  (Bond Market Index Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>061023 - Disclosure - Risk/Return Detail Data {Elements} (Bond Market Index Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000036925Member</Role>
      <ShortName>Risk/Return Detail Data  (Bond Market Index Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>061024 - Document - Risk/Return Summary {Unlabeled} (Diversified Balanced Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000027170Member</Role>
      <ShortName>Risk/Return Summary  (Diversified Balanced Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>061029 - Disclosure - Risk/Return Detail Data {Elements} (Diversified Balanced Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000027170Member</Role>
      <ShortName>Risk/Return Detail Data  (Diversified Balanced Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>061030 - Document - Risk/Return Summary {Unlabeled} (Diversified Growth Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000027171Member</Role>
      <ShortName>Risk/Return Summary  (Diversified Growth Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>061035 - Disclosure - Risk/Return Detail Data {Elements} (Diversified Growth Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000027171Member</Role>
      <ShortName>Risk/Return Detail Data  (Diversified Growth Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>061036 - Document - Risk/Return Summary {Unlabeled} (Diversified Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000036926Member</Role>
      <ShortName>Risk/Return Summary  (Diversified Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>061039 - Disclosure - Risk/Return Detail Data {Elements} (Diversified Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000036926Member</Role>
      <ShortName>Risk/Return Detail Data  (Diversified Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>061040 - Document - Risk/Return Summary {Unlabeled} (Diversified International Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007681Member</Role>
      <ShortName>Risk/Return Summary  (Diversified International Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>061045 - Disclosure - Risk/Return Detail Data {Elements} (Diversified International Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007681Member</Role>
      <ShortName>Risk/Return Detail Data  (Diversified International Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>061046 - Document - Risk/Return Summary {Unlabeled} (Equity Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014083Member</Role>
      <ShortName>Risk/Return Summary  (Equity Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>061051 - Disclosure - Risk/Return Detail Data {Elements} (Equity Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014083Member</Role>
      <ShortName>Risk/Return Detail Data  (Equity Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>061052 - Document - Risk/Return Summary {Unlabeled} (Government &amp; High Quality Bond Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014088Member</Role>
      <ShortName>Risk/Return Summary  (Government &amp; High Quality Bond Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>061057 - Disclosure - Risk/Return Detail Data {Elements} (Government &amp; High Quality Bond Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014088Member</Role>
      <ShortName>Risk/Return Detail Data  (Government &amp; High Quality Bond Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>061058 - Document - Risk/Return Summary {Unlabeled} (Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014086Member</Role>
      <ShortName>Risk/Return Summary  (Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>061063 - Disclosure - Risk/Return Detail Data {Elements} (Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014086Member</Role>
      <ShortName>Risk/Return Detail Data  (Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>061064 - Document - Risk/Return Summary {Unlabeled} (International Emerging Markets Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007656Member</Role>
      <ShortName>Risk/Return Summary  (International Emerging Markets Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>061069 - Disclosure - Risk/Return Detail Data {Elements} (International Emerging Markets Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007656Member</Role>
      <ShortName>Risk/Return Detail Data  (International Emerging Markets Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>061070 - Document - Risk/Return Summary {Unlabeled} (LargeCap Blend Account II)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007658Member</Role>
      <ShortName>Risk/Return Summary  (LargeCap Blend Account II)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>061075 - Disclosure - Risk/Return Detail Data {Elements} (LargeCap Blend Account II)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007658Member</Role>
      <ShortName>Risk/Return Detail Data  (LargeCap Blend Account II)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>061076 - Document - Risk/Return Summary {Unlabeled} (LargeCap Growth Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007685Member</Role>
      <ShortName>Risk/Return Summary  (LargeCap Growth Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>061081 - Disclosure - Risk/Return Detail Data {Elements} (LargeCap Growth Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007685Member</Role>
      <ShortName>Risk/Return Detail Data  (LargeCap Growth Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>061082 - Document - Risk/Return Summary {Unlabeled} (LargeCap Growth Account I)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007682Member</Role>
      <ShortName>Risk/Return Summary  (LargeCap Growth Account I)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>061087 - Disclosure - Risk/Return Detail Data {Elements} (LargeCap Growth Account I)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007682Member</Role>
      <ShortName>Risk/Return Detail Data  (LargeCap Growth Account I)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>061088 - Document - Risk/Return Summary {Unlabeled} (LargeCap S&amp;P 500 Index Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007660Member</Role>
      <ShortName>Risk/Return Summary  (LargeCap S&amp;P 500 Index Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>061093 - Disclosure - Risk/Return Detail Data {Elements} (LargeCap S&amp;P 500 Index Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007660Member</Role>
      <ShortName>Risk/Return Detail Data  (LargeCap S&amp;P 500 Index Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>061094 - Document - Risk/Return Summary {Unlabeled} (LargeCap Value Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007680Member</Role>
      <ShortName>Risk/Return Summary  (LargeCap Value Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>061099 - Disclosure - Risk/Return Detail Data {Elements} (LargeCap Value Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007680Member</Role>
      <ShortName>Risk/Return Detail Data  (LargeCap Value Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>061100 - Document - Risk/Return Summary {Unlabeled} (MidCap Blend Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007662Member</Role>
      <ShortName>Risk/Return Summary  (MidCap Blend Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>061105 - Disclosure - Risk/Return Detail Data {Elements} (MidCap Blend Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007662Member</Role>
      <ShortName>Risk/Return Detail Data  (MidCap Blend Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>061106 - Document - Risk/Return Summary {Unlabeled} (Money Market Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007665Member</Role>
      <ShortName>Risk/Return Summary  (Money Market Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>061111 - Disclosure - Risk/Return Detail Data {Elements} (Money Market Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007665Member</Role>
      <ShortName>Risk/Return Detail Data  (Money Market Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>061112 - Document - Risk/Return Summary {Unlabeled} (Principal Capital Appreciation Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014085Member</Role>
      <ShortName>Risk/Return Summary  (Principal Capital Appreciation Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>061117 - Disclosure - Risk/Return Detail Data {Elements} (Principal Capital Appreciation Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014085Member</Role>
      <ShortName>Risk/Return Detail Data  (Principal Capital Appreciation Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R118.htm</HtmlFileName>
      <LongName>061118 - Document - Risk/Return Summary {Unlabeled} (Principal LifeTime 2010 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007667Member</Role>
      <ShortName>Risk/Return Summary  (Principal LifeTime 2010 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R123.htm</HtmlFileName>
      <LongName>061123 - Disclosure - Risk/Return Detail Data {Elements} (Principal LifeTime 2010 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007667Member</Role>
      <ShortName>Risk/Return Detail Data  (Principal LifeTime 2010 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R124.htm</HtmlFileName>
      <LongName>061124 - Document - Risk/Return Summary {Unlabeled} (Principal LifeTime 2020 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007668Member</Role>
      <ShortName>Risk/Return Summary  (Principal LifeTime 2020 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R129.htm</HtmlFileName>
      <LongName>061129 - Disclosure - Risk/Return Detail Data {Elements} (Principal LifeTime 2020 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007668Member</Role>
      <ShortName>Risk/Return Detail Data  (Principal LifeTime 2020 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R130.htm</HtmlFileName>
      <LongName>061130 - Document - Risk/Return Summary {Unlabeled} (Principal LifeTime 2030 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007669Member</Role>
      <ShortName>Risk/Return Summary  (Principal LifeTime 2030 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R135.htm</HtmlFileName>
      <LongName>061135 - Disclosure - Risk/Return Detail Data {Elements} (Principal LifeTime 2030 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007669Member</Role>
      <ShortName>Risk/Return Detail Data  (Principal LifeTime 2030 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R136.htm</HtmlFileName>
      <LongName>061136 - Document - Risk/Return Summary {Unlabeled} (Principal LifeTime 2040 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007670Member</Role>
      <ShortName>Risk/Return Summary  (Principal LifeTime 2040 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R141.htm</HtmlFileName>
      <LongName>061141 - Disclosure - Risk/Return Detail Data {Elements} (Principal LifeTime 2040 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007670Member</Role>
      <ShortName>Risk/Return Detail Data  (Principal LifeTime 2040 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R142.htm</HtmlFileName>
      <LongName>061142 - Document - Risk/Return Summary {Unlabeled} (Principal LifeTime 2050 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007671Member</Role>
      <ShortName>Risk/Return Summary  (Principal LifeTime 2050 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R147.htm</HtmlFileName>
      <LongName>061147 - Disclosure - Risk/Return Detail Data {Elements} (Principal LifeTime 2050 Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007671Member</Role>
      <ShortName>Risk/Return Detail Data  (Principal LifeTime 2050 Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R148.htm</HtmlFileName>
      <LongName>061148 - Document - Risk/Return Summary {Unlabeled} (Principal LifeTime Strategic Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007672Member</Role>
      <ShortName>Risk/Return Summary  (Principal LifeTime Strategic Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R153.htm</HtmlFileName>
      <LongName>061153 - Disclosure - Risk/Return Detail Data {Elements} (Principal LifeTime Strategic Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007672Member</Role>
      <ShortName>Risk/Return Detail Data  (Principal LifeTime Strategic Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R154.htm</HtmlFileName>
      <LongName>061154 - Document - Risk/Return Summary {Unlabeled} (Real Estate Securities Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007673Member</Role>
      <ShortName>Risk/Return Summary  (Real Estate Securities Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R159.htm</HtmlFileName>
      <LongName>061159 - Disclosure - Risk/Return Detail Data {Elements} (Real Estate Securities Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007673Member</Role>
      <ShortName>Risk/Return Detail Data  (Real Estate Securities Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R160.htm</HtmlFileName>
      <LongName>061160 - Document - Risk/Return Summary {Unlabeled} (Short-Term Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014089Member</Role>
      <ShortName>Risk/Return Summary  (Short-Term Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R165.htm</HtmlFileName>
      <LongName>061165 - Disclosure - Risk/Return Detail Data {Elements} (Short-Term Income Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014089Member</Role>
      <ShortName>Risk/Return Detail Data  (Short-Term Income Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R166.htm</HtmlFileName>
      <LongName>061166 - Document - Risk/Return Summary {Unlabeled} (SmallCap Blend Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007675Member</Role>
      <ShortName>Risk/Return Summary  (SmallCap Blend Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R171.htm</HtmlFileName>
      <LongName>061171 - Disclosure - Risk/Return Detail Data {Elements} (SmallCap Blend Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007675Member</Role>
      <ShortName>Risk/Return Detail Data  (SmallCap Blend Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R172.htm</HtmlFileName>
      <LongName>061172 - Document - Risk/Return Summary {Unlabeled} (SmallCap Growth Account II)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007676Member</Role>
      <ShortName>Risk/Return Summary  (SmallCap Growth Account II)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R177.htm</HtmlFileName>
      <LongName>061177 - Disclosure - Risk/Return Detail Data {Elements} (SmallCap Growth Account II)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007676Member</Role>
      <ShortName>Risk/Return Detail Data  (SmallCap Growth Account II)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R178.htm</HtmlFileName>
      <LongName>061178 - Document - Risk/Return Summary {Unlabeled} (SmallCap Value Account I)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000007678Member</Role>
      <ShortName>Risk/Return Summary  (SmallCap Value Account I)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R183.htm</HtmlFileName>
      <LongName>061183 - Disclosure - Risk/Return Detail Data {Elements} (SmallCap Value Account I)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000007678Member</Role>
      <ShortName>Risk/Return Detail Data  (SmallCap Value Account I)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R184.htm</HtmlFileName>
      <LongName>061184 - Document - Risk/Return Summary {Unlabeled} (Strategic Asset Management Balanced Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014090Member</Role>
      <ShortName>Risk/Return Summary  (Strategic Asset Management Balanced Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R189.htm</HtmlFileName>
      <LongName>061189 - Disclosure - Risk/Return Detail Data {Elements} (Strategic Asset Management Balanced Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014090Member</Role>
      <ShortName>Risk/Return Detail Data  (Strategic Asset Management Balanced Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R190.htm</HtmlFileName>
      <LongName>061190 - Document - Risk/Return Summary {Unlabeled} (Strategic Asset Management Conservative Balanced Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014091Member</Role>
      <ShortName>Risk/Return Summary  (Strategic Asset Management Conservative Balanced Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R195.htm</HtmlFileName>
      <LongName>061195 - Disclosure - Risk/Return Detail Data {Elements} (Strategic Asset Management Conservative Balanced Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014091Member</Role>
      <ShortName>Risk/Return Detail Data  (Strategic Asset Management Conservative Balanced Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R196.htm</HtmlFileName>
      <LongName>061196 - Document - Risk/Return Summary {Unlabeled} (Strategic Asset Management Conservative Growth Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014092Member</Role>
      <ShortName>Risk/Return Summary  (Strategic Asset Management Conservative Growth Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R201.htm</HtmlFileName>
      <LongName>061201 - Disclosure - Risk/Return Detail Data {Elements} (Strategic Asset Management Conservative Growth Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014092Member</Role>
      <ShortName>Risk/Return Detail Data  (Strategic Asset Management Conservative Growth Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R202.htm</HtmlFileName>
      <LongName>061202 - Document - Risk/Return Summary {Unlabeled} (Strategic Asset Management Flexible Income Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014093Member</Role>
      <ShortName>Risk/Return Summary  (Strategic Asset Management Flexible Income Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R207.htm</HtmlFileName>
      <LongName>061207 - Disclosure - Risk/Return Detail Data {Elements} (Strategic Asset Management Flexible Income Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014093Member</Role>
      <ShortName>Risk/Return Detail Data  (Strategic Asset Management Flexible Income Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R208.htm</HtmlFileName>
      <LongName>061208 - Document - Risk/Return Summary {Unlabeled} (Strategic Asset Management Strategic Growth Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturn_S000014084Member</Role>
      <ShortName>Risk/Return Summary  (Strategic Asset Management Strategic Growth Portfolio Account)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R213.htm</HtmlFileName>
      <LongName>061213 - Disclosure - Risk/Return Detail Data {Elements} (Strategic Asset Management Strategic Growth Portfolio Account)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.PrincipalFunds.com/role/RiskReturnDetailData_S000014084Member</Role>
      <ShortName>Risk/Return Detail Data  (Strategic Asset Management Strategic Growth Portfolio Account)</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>ck0000012601-20111231.xml</File>
    <File>ck0000012601-20111231.xsd</File>
    <File>ck0000012601-20111231_cal.xml</File>
    <File>ck0000012601-20111231_def.xml</File>
    <File>ck0000012601-20111231_lab.xml</File>
    <File>ck0000012601-20111231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>BarChart1.jpg</File>
    <File>BarChart2.jpg</File>
    <File>BarChart3.jpg</File>
    <File>BarChart4.jpg</File>
    <File>BarChart5.jpg</File>
    <File>BarChart6.jpg</File>
    <File>BarChart7.jpg</File>
    <File>BarChart8.jpg</File>
    <File>BarChart9.jpg</File>
    <File>BarChart10.jpg</File>
    <File>BarChart11.jpg</File>
    <File>BarChart12.jpg</File>
    <File>BarChart13.jpg</File>
    <File>BarChart14.jpg</File>
    <File>BarChart15.jpg</File>
    <File>BarChart16.jpg</File>
    <File>BarChart17.jpg</File>
    <File>BarChart18.jpg</File>
    <File>BarChart19.jpg</File>
    <File>BarChart20.jpg</File>
    <File>BarChart21.jpg</File>
    <File>BarChart22.jpg</File>
    <File>BarChart23.jpg</File>
    <File>BarChart24.jpg</File>
    <File>BarChart25.jpg</File>
    <File>BarChart26.jpg</File>
    <File>BarChart27.jpg</File>
    <File>BarChart28.jpg</File>
    <File>BarChart29.jpg</File>
    <File>BarChart30.jpg</File>
    <File>BarChart31.jpg</File>
    <File>BarChart32.jpg</File>
    <File>BarChart33.jpg</File>
    <File>BarChart34.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
