<?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>2.2.0.25</Version>
  <ReportType />
  <MyReports>
    <Report>
      <IsDefault>true</IsDefault>
      <ReportType>Sheet</ReportType>
      <LongName>010000 - Document - Risk/Return Summary (ALIMI-S000007186Member) {Unlabeled}</LongName>
      <ShortName>Risk/Return Summary (ALIMI-S000007186Member)</ShortName>
      <Role>http://fidinv/role/ALIMI-S000007186MemberRiskReturn</Role>
      <ContainEmbeddedReports>true</ContainEmbeddedReports>
      <XmlFileName>R1.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ReportType>Sheet</ReportType>
      <LongName>010000 - Document - Risk/Return Summary (ALIM-S000007186Member) {Unlabeled}</LongName>
      <ShortName>Risk/Return Summary (ALIM-S000007186Member)</ShortName>
      <Role>http://fidinv/role/ALIM-S000007186MemberRiskReturn</Role>
      <ContainEmbeddedReports>true</ContainEmbeddedReports>
      <XmlFileName>R2.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ReportType>Sheet</ReportType>
      <LongName>010000 - Document - Risk/Return Summary (LIM-S000007186Member) {Unlabeled}</LongName>
      <ShortName>Risk/Return Summary (LIM-S000007186Member)</ShortName>
      <Role>http://fidinv/role/LIM-S000007186MemberRiskReturn</Role>
      <ContainEmbeddedReports>true</ContainEmbeddedReports>
      <XmlFileName>R3.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ReportType>Sheet</ReportType>
      <LongName>010000 - Document - Risk/Return Summary {Unlabeled}</LongName>
      <ShortName>Risk/Return Summary</ShortName>
      <Role>http://xbrl.sec.gov/rr/role/RiskReturn</Role>
      <ContainEmbeddedReports>true</ContainEmbeddedReports>
      <XmlFileName>R4.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ReportType>Sheet</ReportType>
      <LongName>040000 - Disclosure - Risk/Return Detail Data {Elements}</LongName>
      <ShortName>Risk/Return Detail Data</ShortName>
      <Role>http://xbrl.sec.gov/rr/role/RiskReturnDetailData</Role>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <XmlFileName>R29.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ReportType>Book</ReportType>
      <LongName>All Reports</LongName>
      <ShortName>All Reports</ShortName>
      <Role />
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <XmlFileName />
    </Report>
  </MyReports>
  <EntityCount>1</EntityCount>
  <ContextCount>28</ContextCount>
  <SegmentCount>23</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <UnitCount>4</UnitCount>
  <ElementCount>86</ElementCount>
  <FootnotesReported>true</FootnotesReported>
  <TuplesReported>false</TuplesReported>
  <ContextSummary>
    <ContextSummary>
      <ContextName>ALIMI-fidnperfidx-barclayscapitalyearmunicipalbondindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019666Member</ContextName>
      <ElementCount>33</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007188_C000019672_AfterTaxesOnDistributionsAndSalesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>FSN-S000007188Member</ContextName>
      <ElementCount>40</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>LIM-fidnperfidx-barclayscapitalmunicipalbondindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019670_AfterTaxesOnDistributionsAndSalesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>ALIM-fidnperfidx-barclayscapitalyearmunicipalbondindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019665_AfterTaxesOnDistributionsAndSalesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019668Member</ContextName>
      <ElementCount>31</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019669Member</ContextName>
      <ElementCount>33</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019670_AfterTaxesOnDistributionsMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019667Member</ContextName>
      <ElementCount>31</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>ALIM-S000007186Member</ContextName>
      <ElementCount>38</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>FSN-fidnperfidx-fidelitystrategicincomecompositeindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>LIM-fidnperfidx-barclayscapitalyearmunicipalbondindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019670Member</ContextName>
      <ElementCount>22</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>GLOBAL-CONTEXT</ContextName>
      <ElementCount>7</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>ALIMI-fidnperfidx-barclayscapitalmunicipalbondindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019666_AfterTaxesOnDistributionsAndSalesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>ALIM-fidnperfidx-barclayscapitalmunicipalbondindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019665_AfterTaxesOnDistributionsMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019666_AfterTaxesOnDistributionsMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007188_C000019672_AfterTaxesOnDistributionsMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007188_C000019672Member</ContextName>
      <ElementCount>21</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>FSN-fidnperfidx-thebofamerrilllynchltsupgtsmltsupgtushighyieldconstrainedindexreflectsnodeductionforfeesexpensesortaxesMember</ContextName>
      <ElementCount>3</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>ALIMI-S000007186Member</ContextName>
      <ElementCount>37</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>LIM-S000007186Member</ContextName>
      <ElementCount>41</ElementCount>
    </ContextSummary>
    <ContextSummary>
      <ContextName>S000007186_C000019665Member</ContextName>
      <ElementCount>22</ElementCount>
    </ContextSummary>
  </ContextSummary>
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
