<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.23.4</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>7</ContextCount>
  <ElementCount>64</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>7</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>2</UnitCount>
  <MyReports>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/DocumentInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>000001 - Document - Risk/Return Summary - FidelityLimitedTermGovernmentFund-PRO</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/SummaryS000005156_FidelityLimitedTermGovernmentFund-PRO</Role>
      <ShortName>Risk/Return Summary - FidelityLimitedTermGovernmentFund-PRO</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>000002 - Schedule - Shareholder Fees - FidelityLimitedTermGovernmentFund-PRO</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/ShareholderFeesS000005156_FidelityLimitedTermGovernmentFund-PRO</Role>
      <ShortName>Shareholder Fees - FidelityLimitedTermGovernmentFund-PRO</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>000003 - Schedule - Annual Operating Expenses - FidelityLimitedTermGovernmentFund-PRO</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/OperatingExpensesS000005156_FidelityLimitedTermGovernmentFund-PRO</Role>
      <ShortName>Annual Operating Expenses - FidelityLimitedTermGovernmentFund-PRO</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>000004 - Schedule - Expense Example - FidelityLimitedTermGovernmentFund-PRO</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/ExpenseExampleS000005156_FidelityLimitedTermGovernmentFund-PRO</Role>
      <ShortName>Expense Example - FidelityLimitedTermGovernmentFund-PRO</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>000006 - Schedule - Annual Total Returns - FidelityLimitedTermGovernmentFund-PRO</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/AnnualTotalReturnsBarChartS000005156_FidelityLimitedTermGovernmentFund-PRO</Role>
      <ShortName>Annual Total Returns - FidelityLimitedTermGovernmentFund-PRO</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>000007 - Schedule - Average Annual Total Returns - FidelityLimitedTermGovernmentFund-PRO</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/AverageAnnualTotalReturnsS000005156_FidelityLimitedTermGovernmentFund-PRO</Role>
      <ShortName>Average Annual Total Returns - FidelityLimitedTermGovernmentFund-PRO</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>000009 - Disclosure - Risk/Return Detail Data - FidelityLimitedTermGovernmentFund-PRO</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fidelity.com/role/DisclosureDetailS000005156_FidelityLimitedTermGovernmentFund-PRO</Role>
      <ShortName>Risk/Return Detail Data - FidelityLimitedTermGovernmentFund-PRO</ShortName>
      <MenuCategory>Risk/Return</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="filing7251.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.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>Risk/Return</MenuCategory>
      <Position>9</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="485BPOS" isN1a="true" isRR="true" isRRorOEF="true" original="filing7251.htm">filing7251.htm</File>
    <File>fmr-20240129.xsd</File>
    <File>fmr-20240129_cal.xml</File>
    <File>fmr-20240129_def.xml</File>
    <File>fmr-20240129_lab.xml</File>
    <File>fmr-20240129_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>img94445_1.jpg</File>
    <File>img94446_1.jpg</File>
    <File>img94446_4.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="6">http://xbrl.sec.gov/dei/2022</BaseTaxonomy>
    <BaseTaxonomy items="70">http://xbrl.sec.gov/rr/2022</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
