<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2020-01-31"
  xmlns:iso4217="http://www.xbrl.org/2003/iso4217"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:rr="http://xbrl.sec.gov/rr/2018-01-31"
  xmlns:wpl="http://www.proofPlus.com/20220301"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xhtml="http://www.w3.org/1999/xhtml"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="wpl-20220301.xsd" xlink:type="simple"/>
    <context id="Trust">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000056353Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000056353Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000177580Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000056353_C000177580_ReturnBeforeTaxes_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000056353Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:ReturnBeforeTaxesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000177580Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000056353_C000177580_AfterTaxesOnDistributions_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000056353Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000177580Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000056353_C000177580_AfterTaxesOnDistributionsAndSales_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000056353Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsAndSalesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000177580Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000056353_IndexLB124_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000056353Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:IndexLB124Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInflationProtectedBondIndexFundPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000037003Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInflationProtectedBondIndexFundPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000037003Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000113282Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000037003_C000113282_ReturnBeforeTaxes_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInflationProtectedBondIndexFundPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000037003Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:ReturnBeforeTaxesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000113282Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000037003_C000113282_AfterTaxesOnDistributions_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInflationProtectedBondIndexFundPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000037003Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000113282Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000037003_C000113282_AfterTaxesOnDistributionsAndSales_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInflationProtectedBondIndexFundPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000037003Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsAndSalesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000113282Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000037003_IndexLB124_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInflationProtectedBondIndexFundPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000037003Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:IndexLB124Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInternationalBondIndexFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000066711Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInternationalBondIndexFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000066711Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000214977Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000066711_C000214977_ReturnBeforeTaxes_D1231FidelityInternationalBondIndexFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInternationalBondIndexFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000066711Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:ReturnBeforeTaxesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000214977Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000066711_C000214977_AfterTaxesOnDistributions_D1231FidelityInternationalBondIndexFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInternationalBondIndexFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000066711Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000214977Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000066711_C000214977_AfterTaxesOnDistributionsAndSales_D1231FidelityInternationalBondIndexFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInternationalBondIndexFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000066711Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsAndSalesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000214977Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000066711_IndexIXYYF_D1231FidelityInternationalBondIndexFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelityInternationalBondIndexFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000066711Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:IndexIXYYFMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySAIMunicipalIncomeFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000062002Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySAIMunicipalIncomeFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000062002Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000200824Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000062002_C000200824_ReturnBeforeTaxes_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySAIMunicipalIncomeFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000062002Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:ReturnBeforeTaxesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000200824Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000062002_C000200824_AfterTaxesOnDistributions_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySAIMunicipalIncomeFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000062002Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000200824Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000062002_C000200824_AfterTaxesOnDistributionsAndSales_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySAIMunicipalIncomeFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000062002Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsAndSalesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000200824Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000062002_IndexLB015_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySAIMunicipalIncomeFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000062002Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:IndexLB015Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000062002_IndexLB083_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySAIMunicipalIncomeFundPRO07Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000062002Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:IndexLB083Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000072688Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000072688_C000229123_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000072688Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000229123Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000072689Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000072689Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000229124Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000026423Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000026423Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000079293Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000026423_C000079293_ReturnBeforeTaxes_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000026423Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:ReturnBeforeTaxesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000079293Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000026423_C000079293_AfterTaxesOnDistributions_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000026423Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000079293Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000026423_C000079293_AfterTaxesOnDistributionsAndSales_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000026423Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">rr:AfterTaxesOnDistributionsAndSalesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:ProspectusShareClassAxis">wpl:C000079293Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <context id="S000026423_IndexLB200_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000035315</identifier>
            <segment>
                <xbrldi:explicitMember dimension="dei:DocumentInformationDocumentAxis">wpl:D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="dei:LegalEntityAxis">wpl:S000026423Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="rr:PerformanceMeasureAxis">wpl:IndexLB200Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2022-03-01</startDate>
            <endDate>2022-03-01</endDate>
        </period>
    </context>
    <unit id="usd">
        <measure>iso4217:USD</measure>
    </unit>
    <unit id="pure">
        <measure>pure</measure>
    </unit>
    <dei:DocumentType contextRef="Trust">485BPOS</dei:DocumentType>
    <dei:DocumentPeriodEndDate contextRef="Trust">2021-12-31</dei:DocumentPeriodEndDate>
    <dei:AmendmentFlag contextRef="Trust">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey contextRef="Trust">0000035315</dei:EntityCentralIndexKey>
    <dei:EntityInvCompanyType contextRef="Trust">N-1A</dei:EntityInvCompanyType>
    <rr:AnnualReturn2018
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="INF"
      unitRef="pure">-0.0135</rr:AnnualReturn2018>
    <rr:AnnualReturn2019
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="INF"
      unitRef="pure">0.0838</rr:AnnualReturn2019>
    <rr:AnnualReturn2020
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="INF"
      unitRef="pure">0.1099</rr:AnnualReturn2020>
    <rr:AnnualReturn2021
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="INF"
      unitRef="pure">0.0592</rr:AnnualReturn2021>
    <rr:AnnualReturn2013
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">-0.0863</rr:AnnualReturn2013>
    <rr:AnnualReturn2014
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">0.0369</rr:AnnualReturn2014>
    <rr:AnnualReturn2015
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">-0.0171</rr:AnnualReturn2015>
    <rr:AnnualReturn2016
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">0.0488</rr:AnnualReturn2016>
    <rr:AnnualReturn2017
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">0.0298</rr:AnnualReturn2017>
    <rr:AnnualReturn2018
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">-0.0137</rr:AnnualReturn2018>
    <rr:AnnualReturn2019
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">0.0831</rr:AnnualReturn2019>
    <rr:AnnualReturn2020
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">0.1090</rr:AnnualReturn2020>
    <rr:AnnualReturn2021
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="INF"
      unitRef="pure">0.0593</rr:AnnualReturn2021>
    <rr:AnnualReturn2020
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="INF"
      unitRef="pure">0.0433</rr:AnnualReturn2020>
    <rr:AnnualReturn2021
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="INF"
      unitRef="pure">-0.0174</rr:AnnualReturn2021>
    <rr:AnnualReturn2019
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="INF"
      unitRef="pure">0.0851</rr:AnnualReturn2019>
    <rr:AnnualReturn2020
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="INF"
      unitRef="pure">0.0427</rr:AnnualReturn2020>
    <rr:AnnualReturn2021
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="INF"
      unitRef="pure">0.0233</rr:AnnualReturn2021>
    <rr:AnnualReturn2012
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">0.0477</rr:AnnualReturn2012>
    <rr:AnnualReturn2013
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">-0.0577</rr:AnnualReturn2013>
    <rr:AnnualReturn2014
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">0.0080</rr:AnnualReturn2014>
    <rr:AnnualReturn2015
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">-0.0092</rr:AnnualReturn2015>
    <rr:AnnualReturn2016
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">0.0388</rr:AnnualReturn2016>
    <rr:AnnualReturn2017
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">0.0199</rr:AnnualReturn2017>
    <rr:AnnualReturn2018
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">-0.0042</rr:AnnualReturn2018>
    <rr:AnnualReturn2019
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">0.0689</rr:AnnualReturn2019>
    <rr:AnnualReturn2020
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">0.0826</rr:AnnualReturn2020>
    <rr:AnnualReturn2021
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="INF"
      unitRef="pure">0.0560</rr:AnnualReturn2021>
    <dei:EntityRegistrantName contextRef="Trust">FIDELITY SALEM STREET TRUST</dei:EntityRegistrantName>
    <rr:RiskReturnHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Fund Summary
                  Fund:Fidelity Flex&#xae; Inflation-Protected Bond Index Fund

</rr:RiskReturnHeading>
    <rr:ObjectiveHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Investment Objective

</rr:ObjectiveHeading>
    <rr:ObjectivePrimaryTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         The fund seeks to provide investment results that correspond to the total return of the inflation-protected sector of the
            United States Treasury market.


</rr:ObjectivePrimaryTextBlock>
    <rr:ExpenseHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Fee Table

</rr:ExpenseHeading>
    <rr:ExpenseNarrativeTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

</rr:ExpenseNarrativeTextBlock>
    <rr:ShareholderFeesCaption contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Shareholder fees

</rr:ShareholderFeesCaption>
    <rr:ShareholderFeeOther
      contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="0"
      unitRef="usd">0</rr:ShareholderFeeOther>
    <rr:OperatingExpensesCaption contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">                  Annual Operating Expenses
                  (expenses that you pay each year as a % of the value of your investment)

</rr:OperatingExpensesCaption>
    <rr:ManagementFeesOverAssets
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0</rr:ManagementFeesOverAssets>
    <rr:DistributionAndService12b1FeesOverAssets
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0</rr:DistributionAndService12b1FeesOverAssets>
    <rr:OtherExpensesOverAssets
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0.0000</rr:OtherExpensesOverAssets>
    <rr:ExpensesOverAssets
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      id="id_footnote_elem_778888579_7"
      unitRef="pure">0.0000</rr:ExpensesOverAssets>
    <rr:ExpenseExampleNarrativeTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">                  This example helps compare the cost of investing in the fund with the cost of investing in other funds.

                  Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual
            operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses
            or returns, all of which may vary. This example does not include any fees paid at the fee-based account or plan level. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end
            of each time period indicated:


</rr:ExpenseExampleNarrativeTextBlock>
    <rr:ExpenseExampleYear01
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear01>
    <rr:ExpenseExampleYear03
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear03>
    <rr:ExpenseExampleYear05
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear05>
    <rr:ExpenseExampleYear10
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear10>
    <rr:PortfolioTurnoverHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Portfolio Turnover

</rr:PortfolioTurnoverHeading>
    <rr:PortfolioTurnoverTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are
            held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 28%  of the average value of its portfolio.


</rr:PortfolioTurnoverTextBlock>
    <rr:PortfolioTurnoverRate
      contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0.28</rr:PortfolioTurnoverRate>
    <rr:StrategyHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Principal Investment Strategies

</rr:StrategyHeading>
    <rr:StrategyNarrativeTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
            Normally investing at least 80% of assets in inflation-protected debt securities included in the Bloomberg U.S. Treasury Inflation-Protected
               Securities (TIPS) Index.



            Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest
               rate, total return, and credit default) and futures contracts - and forward-settling securities, to adjust the fund's risk
               exposure.



</rr:StrategyNarrativeTextBlock>
    <rr:RiskHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Principal Investment Risks

</rr:RiskHeading>
    <rr:RiskNarrativeTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">
            Interest Rate Changes.&#160;Interest rate increases can cause the price of a debt security to decrease.



            Prepayment.&#160;The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility
               if interest rates change.



            Issuer-Specific Changes.&#160;The value of an individual security or particular type of security can be more volatile than, and can perform differently
               from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security
               can cause the price of a security to decrease.



            Correlation to Index.&#160;The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund,
               transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions
               from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified
               and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.



            Passive Management Risk.&#160;The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities,
               regardless of the current or projected performance of the fund&#x92;s index or of the actual securities included in the index.
               This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund&#x92;s
               performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities
               or lessen the impact of a market decline or a decline in the value of one or more issuers.



            Leverage Risk.&#160;Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.



            Investing for Inflation Protection.&#160;Increases in real interest rates can cause the price of inflation-protected debt securities to decrease. Interest payments
               on inflation-protected debt securities can be unpredictable.


                  An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.  Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will
            fluctuate. You could lose money by investing in the fund.


</rr:RiskNarrativeTextBlock>
    <rr:RiskNotInsuredDepositoryInstitution contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.</rr:RiskNotInsuredDepositoryInstitution>
    <rr:RiskLoseMoney contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">You could lose money by investing in the fund.</rr:RiskLoseMoney>
    <rr:BarChartAndPerformanceTableHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Performance

</rr:BarChartAndPerformanceTableHeading>
    <rr:PerformanceNarrativeTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">                  The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.  The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.  The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level.

                  Visit www.401k.com and log in  for more recent performance information.


</rr:PerformanceNarrativeTextBlock>
    <rr:PerformanceInformationIllustratesVariabilityOfReturns contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.</rr:PerformanceInformationIllustratesVariabilityOfReturns>
    <rr:PerformancePastDoesNotIndicateFuture contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Past performance (before and after taxes) is not an indication of future performance.</rr:PerformancePastDoesNotIndicateFuture>
    <rr:PerformanceAvailabilityWebSiteAddress contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">www.401k.com and log in</rr:PerformanceAvailabilityWebSiteAddress>
    <rr:BarChartHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Year-by-Year Returns

</rr:BarChartHeading>
    <rr:HighestQuarterlyReturnLabel contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Highest Quarter Return</rr:HighestQuarterlyReturnLabel>
    <rr:BarChartHighestQuarterlyReturn
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0.0406</rr:BarChartHighestQuarterlyReturn>
    <rr:BarChartHighestQuarterlyReturnDate contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">2020-06-30</rr:BarChartHighestQuarterlyReturnDate>
    <rr:LowestQuarterlyReturnLabel contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Lowest Quarter Return</rr:LowestQuarterlyReturnLabel>
    <rr:BarChartLowestQuarterlyReturn
      contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">-0.0150</rr:BarChartLowestQuarterlyReturn>
    <rr:BarChartLowestQuarterlyReturnDate contextRef="S000056353_C000177580_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">2021-03-31</rr:BarChartLowestQuarterlyReturnDate>
    <rr:PerformanceTableHeading contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         Average Annual Returns

</rr:PerformanceTableHeading>
    <rr:PerformanceTableNarrativeTextBlock contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">         After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.  Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).  Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.


</rr:PerformanceTableNarrativeTextBlock>
    <rr:PerformanceTableUsesHighestFederalRate contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.</rr:PerformanceTableUsesHighestFederalRate>
    <rr:PerformanceTableNotRelevantToTaxDeferred contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).</rr:PerformanceTableNotRelevantToTaxDeferred>
    <rr:PerformanceTableExplanationAfterTaxHigher contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.</rr:PerformanceTableExplanationAfterTaxHigher>
    <rr:AverageAnnualReturnLabel contextRef="S000056353_C000177580_ReturnBeforeTaxes_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Return Before Taxes</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000056353_C000177580_ReturnBeforeTaxes_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0.0592</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000056353_C000177580_ReturnBeforeTaxes_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      id="id_footnote_elem_778888887_40"
      unitRef="pure">0.0558</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000056353_C000177580_AfterTaxesOnDistributions_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Return After Taxes on Distributions</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000056353_C000177580_AfterTaxesOnDistributions_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0.0387</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000056353_C000177580_AfterTaxesOnDistributions_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      id="id_footnote_elem_778888887_43"
      unitRef="pure">0.0444</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000056353_C000177580_AfterTaxesOnDistributionsAndSales_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Return After Taxes on Distributions and Sale of Fund Shares</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000056353_C000177580_AfterTaxesOnDistributionsAndSales_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0.0350</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000056353_C000177580_AfterTaxesOnDistributionsAndSales_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      id="id_footnote_elem_778888887_46"
      unitRef="pure">0.0383</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000056353_IndexLB124_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) Index</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000056353_IndexLB124_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      unitRef="pure">0.0596</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000056353_IndexLB124_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member"
      decimals="4"
      id="id_footnote_elem_778888887_49"
      unitRef="pure">0.0562</rr:AverageAnnualReturnSinceInception>
    <rr:AnnualReturnInceptionDate contextRef="S000056353_D1231FidelityFlexInflationProtectedBondIndexFundPRO09Member">2017-03-09</rr:AnnualReturnInceptionDate>
    <rr:RiskReturnHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Fund Summary
                  Fund:Fidelity&#xae; Inflation-Protected Bond Index Fund

</rr:RiskReturnHeading>
    <rr:ObjectiveHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Investment Objective

</rr:ObjectiveHeading>
    <rr:ObjectivePrimaryTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         The fund seeks to provide investment results that correspond to the total return of the inflation-protected sector of the
            United States Treasury market.


</rr:ObjectivePrimaryTextBlock>
    <rr:ExpenseHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Fee Table

</rr:ExpenseHeading>
    <rr:ExpenseNarrativeTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

</rr:ExpenseNarrativeTextBlock>
    <rr:ShareholderFeesCaption contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Shareholder fees

</rr:ShareholderFeesCaption>
    <rr:ShareholderFeeOther
      contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="0"
      unitRef="usd">0</rr:ShareholderFeeOther>
    <rr:OperatingExpensesCaption contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Annual Operating Expenses
                  (expenses that you pay each year as a % of the value of your investment)

</rr:OperatingExpensesCaption>
    <rr:ManagementFeesOverAssets
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0005</rr:ManagementFeesOverAssets>
    <rr:DistributionAndService12b1FeesOverAssets
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0</rr:DistributionAndService12b1FeesOverAssets>
    <rr:OtherExpensesOverAssets
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0000</rr:OtherExpensesOverAssets>
    <rr:ExpensesOverAssets
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0005</rr:ExpensesOverAssets>
    <rr:ExpenseExampleNarrativeTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         This example helps compare the cost of investing in the fund with the cost of investing in other funds.

                  Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual
            operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses
            or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end
            of each time period indicated:


</rr:ExpenseExampleNarrativeTextBlock>
    <rr:ExpenseExampleYear01
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="0"
      unitRef="usd">5</rr:ExpenseExampleYear01>
    <rr:ExpenseExampleYear03
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="0"
      unitRef="usd">16</rr:ExpenseExampleYear03>
    <rr:ExpenseExampleYear05
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="0"
      unitRef="usd">28</rr:ExpenseExampleYear05>
    <rr:ExpenseExampleYear10
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="0"
      unitRef="usd">64</rr:ExpenseExampleYear10>
    <rr:PortfolioTurnoverHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Portfolio Turnover

</rr:PortfolioTurnoverHeading>
    <rr:PortfolioTurnoverTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are
            held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 22%  of the average value of its portfolio.


</rr:PortfolioTurnoverTextBlock>
    <rr:PortfolioTurnoverRate
      contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.22</rr:PortfolioTurnoverRate>
    <rr:StrategyHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Principal Investment Strategies

</rr:StrategyHeading>
    <rr:StrategyNarrativeTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
            Normally investing at least 80% of assets in inflation-protected debt securities included in the Bloomberg U.S. Treasury Inflation-Protected
               Securities (TIPS) Index.



            Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest
               rate, total return, and credit default) and futures contracts - and forward-settling securities, to adjust the fund's risk
               exposure.



</rr:StrategyNarrativeTextBlock>
    <rr:RiskHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Principal Investment Risks

</rr:RiskHeading>
    <rr:RiskNarrativeTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">
            Interest Rate Changes.&#160;Interest rate increases can cause the price of a debt security to decrease.



            Prepayment.&#160;The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility
               if interest rates change.



            Issuer-Specific Changes.&#160;The value of an individual security or particular type of security can be more volatile than, and can perform differently
               from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security
               can cause the price of a security to decrease.



            Correlation to Index.&#160;The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund,
               transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions
               from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified
               and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.



            Passive Management Risk.&#160;The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities,
               regardless of the current or projected performance of the fund&#x92;s index or of the actual securities included in the index.
               This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund&#x92;s
               performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities
               or lessen the impact of a market decline or a decline in the value of one or more issuers.



            Leverage Risk.&#160;Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.



            Investing for Inflation Protection.&#160;Increases in real interest rates can cause the price of inflation-protected debt securities to decrease. Interest payments
               on inflation-protected debt securities can be unpredictable.


                  An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.  Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will
            fluctuate. You could lose money by investing in the fund.


</rr:RiskNarrativeTextBlock>
    <rr:RiskNotInsuredDepositoryInstitution contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.</rr:RiskNotInsuredDepositoryInstitution>
    <rr:RiskLoseMoney contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">You could lose money by investing in the fund.</rr:RiskLoseMoney>
    <rr:BarChartAndPerformanceTableHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Performance

</rr:BarChartAndPerformanceTableHeading>
    <rr:PerformanceNarrativeTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">                  The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.  The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

                  Visit www.fidelity.com  for more recent performance information.


</rr:PerformanceNarrativeTextBlock>
    <rr:PerformanceInformationIllustratesVariabilityOfReturns contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.</rr:PerformanceInformationIllustratesVariabilityOfReturns>
    <rr:PerformancePastDoesNotIndicateFuture contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Past performance (before and after taxes) is not an indication of future performance.</rr:PerformancePastDoesNotIndicateFuture>
    <rr:PerformanceAvailabilityWebSiteAddress contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">www.fidelity.com</rr:PerformanceAvailabilityWebSiteAddress>
    <rr:BarChartHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         Year-by-Year Returns

</rr:BarChartHeading>
    <rr:HighestQuarterlyReturnLabel contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Highest Quarter Return</rr:HighestQuarterlyReturnLabel>
    <rr:BarChartHighestQuarterlyReturn
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0460</rr:BarChartHighestQuarterlyReturn>
    <rr:BarChartHighestQuarterlyReturnDate contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member">2016-03-31</rr:BarChartHighestQuarterlyReturnDate>
    <rr:LowestQuarterlyReturnLabel contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Lowest Quarter Return</rr:LowestQuarterlyReturnLabel>
    <rr:BarChartLowestQuarterlyReturn
      contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">-0.0712</rr:BarChartLowestQuarterlyReturn>
    <rr:BarChartLowestQuarterlyReturnDate contextRef="S000037003_C000113282_D1231FidelityInflationProtectedBondIndexFundPRO10Member">2013-06-30</rr:BarChartLowestQuarterlyReturnDate>
    <rr:PerformanceTableHeading contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Average Annual Returns

</rr:PerformanceTableHeading>
    <rr:PerformanceTableNarrativeTextBlock contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">         After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.  Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).  Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.


</rr:PerformanceTableNarrativeTextBlock>
    <rr:PerformanceTableUsesHighestFederalRate contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.</rr:PerformanceTableUsesHighestFederalRate>
    <rr:PerformanceTableNotRelevantToTaxDeferred contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).</rr:PerformanceTableNotRelevantToTaxDeferred>
    <rr:PerformanceTableExplanationAfterTaxHigher contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.</rr:PerformanceTableExplanationAfterTaxHigher>
    <rr:AverageAnnualReturnLabel contextRef="S000037003_C000113282_ReturnBeforeTaxes_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Return Before Taxes</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000037003_C000113282_ReturnBeforeTaxes_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0593</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000037003_C000113282_ReturnBeforeTaxes_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0526</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000037003_C000113282_ReturnBeforeTaxes_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      id="id_footnote_elem_780049143_95"
      unitRef="pure">0.0280</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000037003_C000113282_AfterTaxesOnDistributions_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Return After Taxes on Distributions</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000037003_C000113282_AfterTaxesOnDistributions_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0395</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000037003_C000113282_AfterTaxesOnDistributions_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0429</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000037003_C000113282_AfterTaxesOnDistributions_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      id="id_footnote_elem_780049143_99"
      unitRef="pure">0.0213</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000037003_C000113282_AfterTaxesOnDistributionsAndSales_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Return After Taxes on Distributions and Sale of Fund Shares</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000037003_C000113282_AfterTaxesOnDistributionsAndSales_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0350</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000037003_C000113282_AfterTaxesOnDistributionsAndSales_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0365</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000037003_C000113282_AfterTaxesOnDistributionsAndSales_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      id="id_footnote_elem_780049143_103"
      unitRef="pure">0.0187</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000037003_IndexLB124_D1231FidelityInflationProtectedBondIndexFundPRO10Member">Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) Index</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000037003_IndexLB124_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0596</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000037003_IndexLB124_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      unitRef="pure">0.0534</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000037003_IndexLB124_D1231FidelityInflationProtectedBondIndexFundPRO10Member"
      decimals="4"
      id="id_footnote_elem_780049143_107"
      unitRef="pure">0.0285</rr:AverageAnnualReturnSinceInception>
    <rr:AnnualReturnInceptionDate contextRef="S000037003_D1231FidelityInflationProtectedBondIndexFundPRO10Member">2012-05-16</rr:AnnualReturnInceptionDate>
    <rr:RiskReturnHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Fund Summary
                  Fund:Fidelity&#xae; International Bond Index Fund

</rr:RiskReturnHeading>
    <rr:ObjectiveHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Investment Objective

</rr:ObjectiveHeading>
    <rr:ObjectivePrimaryTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         The fund seeks to provide a high level of current income.

</rr:ObjectivePrimaryTextBlock>
    <rr:ExpenseHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Fee Table

</rr:ExpenseHeading>
    <rr:ExpenseNarrativeTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

</rr:ExpenseNarrativeTextBlock>
    <rr:ShareholderFeesCaption contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Shareholder fees

</rr:ShareholderFeesCaption>
    <rr:ShareholderFeeOther
      contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="0"
      unitRef="usd">0</rr:ShareholderFeeOther>
    <rr:OperatingExpensesCaption contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">                  Annual Operating Expenses
                  (expenses that you pay each year as a % of the value of your investment)

</rr:OperatingExpensesCaption>
    <rr:ManagementFeesOverAssets
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0006</rr:ManagementFeesOverAssets>
    <rr:DistributionAndService12b1FeesOverAssets
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">0</rr:DistributionAndService12b1FeesOverAssets>
    <rr:OtherExpensesOverAssets
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0000</rr:OtherExpensesOverAssets>
    <rr:ExpensesOverAssets
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0006</rr:ExpensesOverAssets>
    <rr:ExpenseExampleNarrativeTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">                  This example helps compare the cost of investing in the fund with the cost of investing in other funds.

                  Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual
            operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses
            or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end
            of each time period indicated:


</rr:ExpenseExampleNarrativeTextBlock>
    <rr:ExpenseExampleYear01
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="0"
      unitRef="usd">6</rr:ExpenseExampleYear01>
    <rr:ExpenseExampleYear03
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="0"
      unitRef="usd">19</rr:ExpenseExampleYear03>
    <rr:ExpenseExampleYear05
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="0"
      unitRef="usd">34</rr:ExpenseExampleYear05>
    <rr:ExpenseExampleYear10
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="0"
      unitRef="usd">77</rr:ExpenseExampleYear10>
    <rr:PortfolioTurnoverHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">Portfolio Turnover

</rr:PortfolioTurnoverHeading>
    <rr:PortfolioTurnoverTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are
            held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 18%  of the average value of its portfolio.


</rr:PortfolioTurnoverTextBlock>
    <rr:PortfolioTurnoverRate
      contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">0.18</rr:PortfolioTurnoverRate>
    <rr:StrategyHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Principal Investment Strategies

</rr:StrategyHeading>
    <rr:StrategyNarrativeTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">
            Normally investing at least 80% of assets in securities included in the Bloomberg Global Aggregate ex-USD Float Adjusted RIC
               Diversified Index (Hedged USD), which is a multi-currency benchmark that includes fixed-rate treasury, government-related,
               corporate and securitized bonds from developed and emerging markets issuers while excluding USD denominated debt.



            Using statistical sampling techniques based on duration, maturity, interest rate sensitivity, security structure, and credit
               quality to attempt to replicate the returns of the Bloomberg Global Aggregate ex-USD Float Adjusted RIC Diversified Index
               (Hedged USD) using a smaller number of securities.



            Hedging the fund's foreign currency exposures utilizing forward foreign currency exchange contracts.


            Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest
               rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's
               risk exposure.



</rr:StrategyNarrativeTextBlock>
    <rr:RiskHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Principal Investment Risks

</rr:RiskHeading>
    <rr:RiskNarrativeTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">
            Interest Rate Changes.&#160;Interest rate increases can cause the price of a debt security to decrease.



            Foreign Exposure.&#160;Foreign markets, particularly emerging markets, can be more volatile than the U.S. market due to increased risks of adverse
               issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market. The extent of economic development; political stability; market depth, infrastructure, and capitalization; and regulatory
               oversight can be less than in more developed markets. Emerging markets typically have less established legal, accounting and
               financial reporting systems than those in more developed markets, which may reduce the scope or quality of financial information
               available to investors. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties
               and can be extremely volatile. Foreign exchange rates also can be extremely volatile.



            Foreign Currency Transactions.&#160;Although a forward foreign currency exchange contract is used to reduce or hedge a fund&#x92;s exposure to changes in the
               value of the currency, suitable hedging transactions may not be available in all circumstances, may not be successful, and
               may eliminate any chance for the fund to benefit from favorable fluctuations in relevant foreign currencies.



            Prepayment.&#160;The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility
               if interest rates change.



            Issuer-Specific Changes.&#160;The value of an individual security or particular type of security can be more volatile than, and can perform differently
               from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security
               can cause the price of a security to decrease.



            Correlation to Index.&#160;The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund,
               transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions
               from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified
               and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.



            Passive Management Risk.&#160;The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities,
               regardless of the current or projected performance of the fund's index or of the actual securities included in the index.
               This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund's
               performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities
               or lessen the impact of a market decline or a decline in the value of one or more issuers. The fund will be concentrated to
               approximately the same extent that the fund's index concentrates in the securities of issuers in a particular industry.



            Leverage Risk.&#160;Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.


                  In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that
               it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified
               fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than
               would occur in a more diversified fund.

         An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.  Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will
            fluctuate. You could lose money by investing in the fund.


</rr:RiskNarrativeTextBlock>
    <rr:RiskNondiversifiedStatus contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that
               it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified
               fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than
               would occur in a more diversified fund.</rr:RiskNondiversifiedStatus>
    <rr:RiskNotInsuredDepositoryInstitution contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.</rr:RiskNotInsuredDepositoryInstitution>
    <rr:RiskLoseMoney contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">You could lose money by investing in the fund.</rr:RiskLoseMoney>
    <rr:BarChartAndPerformanceTableHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Performance

</rr:BarChartAndPerformanceTableHeading>
    <rr:PerformanceNarrativeTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">                  The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.  The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

                  Visit www.fidelity.com  for more recent performance information.


</rr:PerformanceNarrativeTextBlock>
    <rr:PerformanceInformationIllustratesVariabilityOfReturns contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.</rr:PerformanceInformationIllustratesVariabilityOfReturns>
    <rr:PerformancePastDoesNotIndicateFuture contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">Past performance (before and after taxes) is not an indication of future performance.</rr:PerformancePastDoesNotIndicateFuture>
    <rr:PerformanceAvailabilityWebSiteAddress contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">www.fidelity.com</rr:PerformanceAvailabilityWebSiteAddress>
    <rr:BarChartHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Year-by-Year Returns

</rr:BarChartHeading>
    <rr:HighestQuarterlyReturnLabel contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member">Highest Quarter Return</rr:HighestQuarterlyReturnLabel>
    <rr:BarChartHighestQuarterlyReturn
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0243</rr:BarChartHighestQuarterlyReturn>
    <rr:BarChartHighestQuarterlyReturnDate contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member">2020-06-30</rr:BarChartHighestQuarterlyReturnDate>
    <rr:LowestQuarterlyReturnLabel contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member">Lowest Quarter Return</rr:LowestQuarterlyReturnLabel>
    <rr:BarChartLowestQuarterlyReturn
      contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">-0.0186</rr:BarChartLowestQuarterlyReturn>
    <rr:BarChartLowestQuarterlyReturnDate contextRef="S000066711_C000214977_D1231FidelityInternationalBondIndexFundPRO07Member">2021-03-31</rr:BarChartLowestQuarterlyReturnDate>
    <rr:PerformanceTableHeading contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         Average Annual Returns

</rr:PerformanceTableHeading>
    <rr:PerformanceTableNarrativeTextBlock contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">         After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.  Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).  Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.


</rr:PerformanceTableNarrativeTextBlock>
    <rr:PerformanceTableUsesHighestFederalRate contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.</rr:PerformanceTableUsesHighestFederalRate>
    <rr:PerformanceTableNotRelevantToTaxDeferred contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).</rr:PerformanceTableNotRelevantToTaxDeferred>
    <rr:PerformanceTableExplanationAfterTaxHigher contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.</rr:PerformanceTableExplanationAfterTaxHigher>
    <rr:AverageAnnualReturnLabel contextRef="S000066711_C000214977_ReturnBeforeTaxes_D1231FidelityInternationalBondIndexFundPRO07Member">Return Before Taxes</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000066711_C000214977_ReturnBeforeTaxes_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">-0.0174</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000066711_C000214977_ReturnBeforeTaxes_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_780042260_146"
      unitRef="pure">0.0060</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000066711_C000214977_AfterTaxesOnDistributions_D1231FidelityInternationalBondIndexFundPRO07Member">Return After Taxes on Distributions</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000066711_C000214977_AfterTaxesOnDistributions_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">-0.0199</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000066711_C000214977_AfterTaxesOnDistributions_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_780042260_149"
      unitRef="pure">0.0032</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000066711_C000214977_AfterTaxesOnDistributionsAndSales_D1231FidelityInternationalBondIndexFundPRO07Member">Return After Taxes on Distributions and Sale of Fund Shares</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000066711_C000214977_AfterTaxesOnDistributionsAndSales_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">-0.0103</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000066711_C000214977_AfterTaxesOnDistributionsAndSales_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_780042260_152"
      unitRef="pure">0.0034</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000066711_IndexIXYYF_D1231FidelityInternationalBondIndexFundPRO07Member">Bloomberg Global Aggregate ex-USD Float Adjusted RIC Diversified Index (Hedged USD)</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000066711_IndexIXYYF_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      unitRef="pure">-0.0147</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000066711_IndexIXYYF_D1231FidelityInternationalBondIndexFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_780042260_155"
      unitRef="pure">0.0088</rr:AverageAnnualReturnSinceInception>
    <rr:AnnualReturnInceptionDate contextRef="S000066711_D1231FidelityInternationalBondIndexFundPRO07Member">2019-10-10</rr:AnnualReturnInceptionDate>
    <rr:RiskReturnHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Fund Summary
                  Fund:Fidelity&#xae; SAI Municipal Income Fund

</rr:RiskReturnHeading>
    <rr:ObjectiveHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Investment Objective

</rr:ObjectiveHeading>
    <rr:ObjectivePrimaryTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         The fund seeks to provide a high current yield exempt from federal income tax.

</rr:ObjectivePrimaryTextBlock>
    <rr:ExpenseHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Fee Table

</rr:ExpenseHeading>
    <rr:ExpenseNarrativeTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

</rr:ExpenseNarrativeTextBlock>
    <rr:ShareholderFeesCaption contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Shareholder fees

</rr:ShareholderFeesCaption>
    <rr:ShareholderFeeOther
      contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="0"
      unitRef="usd">0</rr:ShareholderFeeOther>
    <rr:OperatingExpensesCaption contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">                  Annual Operating Expenses
                  (expenses that you pay each year as a % of the value of your investment)

</rr:OperatingExpensesCaption>
    <rr:ManagementFeesOverAssets
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0035</rr:ManagementFeesOverAssets>
    <rr:DistributionAndService12b1FeesOverAssets
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0</rr:DistributionAndService12b1FeesOverAssets>
    <rr:OtherExpensesOverAssets
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0001</rr:OtherExpensesOverAssets>
    <rr:ExpensesOverAssets
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0036</rr:ExpensesOverAssets>
    <rr:ExpenseExampleNarrativeTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">                  This example helps compare the cost of investing in the fund with the cost of investing in other funds.

                  Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual
            operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses
            or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end
            of each time period indicated:


</rr:ExpenseExampleNarrativeTextBlock>
    <rr:ExpenseExampleYear01
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="0"
      unitRef="usd">37</rr:ExpenseExampleYear01>
    <rr:ExpenseExampleYear03
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="0"
      unitRef="usd">116</rr:ExpenseExampleYear03>
    <rr:ExpenseExampleYear05
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="0"
      unitRef="usd">202</rr:ExpenseExampleYear05>
    <rr:ExpenseExampleYear10
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="0"
      unitRef="usd">456</rr:ExpenseExampleYear10>
    <rr:PortfolioTurnoverHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Portfolio Turnover

</rr:PortfolioTurnoverHeading>
    <rr:PortfolioTurnoverTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are
            held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 4%  of the average value of its portfolio.


</rr:PortfolioTurnoverTextBlock>
    <rr:PortfolioTurnoverRate
      contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.04</rr:PortfolioTurnoverRate>
    <rr:StrategyHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Principal Investment Strategies

</rr:StrategyHeading>
    <rr:StrategyNarrativeTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
            Normally investing at least 80% of assets in investment-grade municipal securities whose interest is exempt from federal income
               tax.



            Managing the fund to have similar overall interest rate risk to an index designed to represent Fidelity Management &amp; Research
               Company LLC (FMR)'s view of how the fund's competitive universe will perform over time.



            Allocating assets across different market sectors and maturities.


            Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects.


            Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading
               opportunities to select investments.



</rr:StrategyNarrativeTextBlock>
    <rr:RiskHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Principal Investment Risks

</rr:RiskHeading>
    <rr:RiskNarrativeTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">
            Municipal Market Volatility.&#160;The municipal market is volatile and can be significantly affected by adverse tax, legislative, or political changes and the
               financial condition of the issuers of municipal securities.



            Interest Rate Changes.&#160;Interest rate increases can cause the price of a debt security to decrease.



            Issuer-Specific Changes.&#160;The value of an individual security or particular type of security can be more volatile than, and can perform differently
               from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security
               can cause the price of a security to decrease.


                  An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.  Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will
            fluctuate. You could lose money by investing in the fund.


</rr:RiskNarrativeTextBlock>
    <rr:RiskNotInsuredDepositoryInstitution contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.</rr:RiskNotInsuredDepositoryInstitution>
    <rr:RiskLoseMoney contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">You could lose money by investing in the fund.</rr:RiskLoseMoney>
    <rr:BarChartAndPerformanceTableHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Performance

</rr:BarChartAndPerformanceTableHeading>
    <rr:PerformanceNarrativeTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">                  The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index and an additional index over various periods of time.  The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional
            Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

                  Visit www.fidelity.com  for more recent performance information.


</rr:PerformanceNarrativeTextBlock>
    <rr:PerformanceInformationIllustratesVariabilityOfReturns contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index and an additional index over various periods of time.</rr:PerformanceInformationIllustratesVariabilityOfReturns>
    <rr:PerformancePastDoesNotIndicateFuture contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Past performance (before and after taxes) is not an indication of future performance.</rr:PerformancePastDoesNotIndicateFuture>
    <rr:PerformanceAvailabilityWebSiteAddress contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">www.fidelity.com</rr:PerformanceAvailabilityWebSiteAddress>
    <rr:BarChartHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         Year-by-Year Returns

</rr:BarChartHeading>
    <rr:HighestQuarterlyReturnLabel contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Highest Quarter Return</rr:HighestQuarterlyReturnLabel>
    <rr:BarChartHighestQuarterlyReturn
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0320</rr:BarChartHighestQuarterlyReturn>
    <rr:BarChartHighestQuarterlyReturnDate contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member">2019-03-31</rr:BarChartHighestQuarterlyReturnDate>
    <rr:LowestQuarterlyReturnLabel contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Lowest Quarter Return</rr:LowestQuarterlyReturnLabel>
    <rr:BarChartLowestQuarterlyReturn
      contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">-0.0203</rr:BarChartLowestQuarterlyReturn>
    <rr:BarChartLowestQuarterlyReturnDate contextRef="S000062002_C000200824_D1231FidelitySAIMunicipalIncomeFundPRO07Member">2020-03-31</rr:BarChartLowestQuarterlyReturnDate>
    <rr:PerformanceTableHeading contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Average Annual Returns

</rr:PerformanceTableHeading>
    <rr:PerformanceTableNarrativeTextBlock contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">         After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.  Actual after-tax returns may differ depending on your individual circumstances. Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.


</rr:PerformanceTableNarrativeTextBlock>
    <rr:PerformanceTableUsesHighestFederalRate contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.</rr:PerformanceTableUsesHighestFederalRate>
    <rr:PerformanceTableExplanationAfterTaxHigher contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.</rr:PerformanceTableExplanationAfterTaxHigher>
    <rr:AverageAnnualReturnLabel contextRef="S000062002_C000200824_ReturnBeforeTaxes_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Return Before Taxes</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000062002_C000200824_ReturnBeforeTaxes_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0233</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000062002_C000200824_ReturnBeforeTaxes_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_779401293_193"
      unitRef="pure">0.0546</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000062002_C000200824_AfterTaxesOnDistributions_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Return After Taxes on Distributions</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000062002_C000200824_AfterTaxesOnDistributions_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0230</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000062002_C000200824_AfterTaxesOnDistributions_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_779401293_196"
      unitRef="pure">0.0536</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000062002_C000200824_AfterTaxesOnDistributionsAndSales_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Return After Taxes on Distributions and Sale of Fund Shares</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000062002_C000200824_AfterTaxesOnDistributionsAndSales_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0218</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000062002_C000200824_AfterTaxesOnDistributionsAndSales_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_779401293_199"
      unitRef="pure">0.0477</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000062002_IndexLB015_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Bloomberg Municipal Bond Index</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000062002_IndexLB015_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0152</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000062002_IndexLB015_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_779401293_202"
      unitRef="pure">0.0489</rr:AverageAnnualReturnSinceInception>
    <rr:AverageAnnualReturnLabel contextRef="S000062002_IndexLB083_D1231FidelitySAIMunicipalIncomeFundPRO07Member">Bloomberg 3+ Year Municipal Bond Index</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000062002_IndexLB083_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      unitRef="pure">0.0169</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnSinceInception
      contextRef="S000062002_IndexLB083_D1231FidelitySAIMunicipalIncomeFundPRO07Member"
      decimals="4"
      id="id_footnote_elem_779401293_205"
      unitRef="pure">0.0530</rr:AverageAnnualReturnSinceInception>
    <rr:AnnualReturnInceptionDate contextRef="S000062002_D1231FidelitySAIMunicipalIncomeFundPRO07Member">2018-10-02</rr:AnnualReturnInceptionDate>
    <rr:RiskReturnHeading contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Fund Summary
                  Fund:Fidelity&#xae; Series 0-5 Year Inflation-Protected Bond Index Fund

</rr:RiskReturnHeading>
    <rr:ObjectiveHeading contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Investment Objective

</rr:ObjectiveHeading>
    <rr:ObjectivePrimaryTextBlock contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         The fund seeks to provide investment results that correspond to the total return of the inflation-protected sector of the
            United States Treasury market.


</rr:ObjectivePrimaryTextBlock>
    <rr:ExpenseHeading contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Fee Table

</rr:ExpenseHeading>
    <rr:ExpenseNarrativeTextBlock contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

</rr:ExpenseNarrativeTextBlock>
    <rr:ShareholderFeesCaption contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Shareholder fees

</rr:ShareholderFeesCaption>
    <rr:ShareholderFeeOther
      contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ShareholderFeeOther>
    <rr:OperatingExpensesCaption contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">                  Annual Operating Expenses
                  (expenses that you pay each year as a % of the value of your investment)

</rr:OperatingExpensesCaption>
    <rr:ManagementFeesOverAssets
      contextRef="S000072688_C000229123_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0</rr:ManagementFeesOverAssets>
    <rr:DistributionAndService12b1FeesOverAssets
      contextRef="S000072688_C000229123_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0</rr:DistributionAndService12b1FeesOverAssets>
    <rr:OtherExpensesOverAssets
      contextRef="S000072688_C000229123_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      id="id_footnote_elem_780494553_212"
      unitRef="pure">0.0000</rr:OtherExpensesOverAssets>
    <rr:ExpensesOverAssets
      contextRef="S000072688_C000229123_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0.0000</rr:ExpensesOverAssets>
    <rr:OtherExpensesNewFundBasedOnEstimates contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">Based on estimated amounts for the current fiscal year.</rr:OtherExpensesNewFundBasedOnEstimates>
    <rr:ExpenseExampleNarrativeTextBlock contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">                  This example helps compare the cost of investing in the fund with the cost of investing in other funds.

                  Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual
            operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses
            or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end
            of each time period indicated:


</rr:ExpenseExampleNarrativeTextBlock>
    <rr:ExpenseExampleYear01
      contextRef="S000072688_C000229123_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear01>
    <rr:ExpenseExampleYear03
      contextRef="S000072688_C000229123_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear03>
    <rr:PortfolioTurnoverHeading contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">Portfolio Turnover

</rr:PortfolioTurnoverHeading>
    <rr:PortfolioTurnoverTextBlock contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are
            held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. For the period from August 13, 2021 to December 31, 2021, the fund's portfolio turnover rate was 33%  of the average value of its portfolio.


</rr:PortfolioTurnoverTextBlock>
    <rr:PortfolioTurnoverRate
      contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0.33</rr:PortfolioTurnoverRate>
    <rr:StrategyHeading contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Principal Investment Strategies

</rr:StrategyHeading>
    <rr:StrategyNarrativeTextBlock contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
            Normally investing at least 80% of assets in inflation-protected debt securities included in the Bloomberg US Treasury Inflation-Protected
               Securities (TIPS) 0-5 Years Index, which is composed of inflation-protected debt securities issued by the U.S. Treasury with
               remaining maturities of less than 5 years.



            Using statistical sampling techniques based on duration, maturity, interest rate sensitivity, security structure, and credit
               quality to attempt to replicate the returns of the Bloomberg US Treasury Inflation-Protected Securities (TIPS) 0-5 Years Index
               using a smaller number of securities.



            Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest
               rate, total return, and credit default) and futures contracts - and forward-settling securities, to adjust the fund's risk
               exposure.



</rr:StrategyNarrativeTextBlock>
    <rr:RiskHeading contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Principal Investment Risks

</rr:RiskHeading>
    <rr:RiskNarrativeTextBlock contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
            Interest Rate Changes.&#160;Interest rate increases can cause the price of a debt security to decrease.



            Issuer-Specific Changes.&#160;The value of an individual security or particular type of security can be more volatile than, and can perform differently
               from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security
               can cause the price of a security to decrease.



            Correlation to Index.&#160;The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund,
               transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions
               from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified
               and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.



            Passive Management Risk.&#160;The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities,
               regardless of the current or projected performance of the fund&#x92;s index or of the actual securities included in the index.
               This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund&#x92;s
               performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities
               or lessen the impact of a market decline or a decline in the value of one or more issuers.



            Leverage Risk.&#160;Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.



            Investing for Inflation Protection.&#160;Increases in real interest rates can cause the price of inflation-protected debt securities to decrease. Interest payments
               on inflation-protected debt securities can be unpredictable.


                  An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.  Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will
            fluctuate. You could lose money by investing in the fund.


</rr:RiskNarrativeTextBlock>
    <rr:RiskNotInsuredDepositoryInstitution contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.</rr:RiskNotInsuredDepositoryInstitution>
    <rr:RiskLoseMoney contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">You could lose money by investing in the fund.</rr:RiskLoseMoney>
    <rr:BarChartAndPerformanceTableHeading contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Performance

</rr:BarChartAndPerformanceTableHeading>
    <rr:PerformanceOneYearOrLess contextRef="S000072688_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">Performance history will be available for the fund after the fund has been in operation for one calendar year.</rr:PerformanceOneYearOrLess>
    <rr:RiskReturnHeading contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">                  Fund Summary
                  Fund:Fidelity&#xae; Series 5+ Year Inflation-Protected Bond Index Fund

</rr:RiskReturnHeading>
    <rr:ObjectiveHeading contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Investment Objective

</rr:ObjectiveHeading>
    <rr:ObjectivePrimaryTextBlock contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         The fund seeks to provide investment results that correspond to the total return of the inflation-protected sector of the
            United States Treasury market.


</rr:ObjectivePrimaryTextBlock>
    <rr:ExpenseHeading contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Fee Table

</rr:ExpenseHeading>
    <rr:ExpenseNarrativeTextBlock contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

</rr:ExpenseNarrativeTextBlock>
    <rr:ShareholderFeesCaption contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Shareholder fees

</rr:ShareholderFeesCaption>
    <rr:ShareholderFeeOther
      contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ShareholderFeeOther>
    <rr:OperatingExpensesCaption contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">                  Annual Operating Expenses
                  (expenses that you pay each year as a % of the value of your investment)

</rr:OperatingExpensesCaption>
    <rr:ManagementFeesOverAssets
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0</rr:ManagementFeesOverAssets>
    <rr:DistributionAndService12b1FeesOverAssets
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0</rr:DistributionAndService12b1FeesOverAssets>
    <rr:OtherExpensesOverAssets
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      id="id_footnote_elem_780494925_230"
      unitRef="pure">0.0000</rr:OtherExpensesOverAssets>
    <rr:ExpensesOverAssets
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0.0000</rr:ExpensesOverAssets>
    <rr:OtherExpensesNewFundBasedOnEstimates contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">Based on estimated amounts for the current fiscal year.</rr:OtherExpensesNewFundBasedOnEstimates>
    <rr:ExpenseExampleNarrativeTextBlock contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">                  This example helps compare the cost of investing in the fund with the cost of investing in other funds.

                  Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual
            operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses
            or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end
            of each time period indicated:


</rr:ExpenseExampleNarrativeTextBlock>
    <rr:ExpenseExampleYear01
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear01>
    <rr:ExpenseExampleYear03
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear03>
    <rr:ExpenseExampleYear05
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear05>
    <rr:ExpenseExampleYear10
      contextRef="S000072689_C000229124_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear10>
    <rr:PortfolioTurnoverHeading contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Portfolio Turnover

</rr:PortfolioTurnoverHeading>
    <rr:PortfolioTurnoverTextBlock contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are
            held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. For the period from August 13, 2021 to December 31, 2021, the fund's portfolio turnover rate was 31% ( annualized) of the average value of its portfolio.


</rr:PortfolioTurnoverTextBlock>
    <rr:PortfolioTurnoverRate
      contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member"
      decimals="4"
      unitRef="pure">0.31</rr:PortfolioTurnoverRate>
    <rr:StrategyHeading contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Principal Investment Strategies

</rr:StrategyHeading>
    <rr:StrategyNarrativeTextBlock contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
            Normally investing at least 80% of assets in inflation-protected debt securities included in the Bloomberg US Treasury Inflation-Protected
               Securities (TIPS) 5+ Years Index, which is composed of inflation-protected debt securities issued by the U.S. Treasury with
               remaining maturities of 5 or more years.



            Using statistical sampling techniques based on duration, maturity, interest rate sensitivity, security structure, and credit
               quality to attempt to replicate the returns of the Bloomberg US Treasury Inflation-Protected Securities (TIPS) 5+ Years Index
               using a smaller number of securities.



            Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest
               rate, total return, and credit default) and futures contracts - and forward-settling securities, to adjust the fund's risk
               exposure.



</rr:StrategyNarrativeTextBlock>
    <rr:RiskHeading contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Principal Investment Risks

</rr:RiskHeading>
    <rr:RiskNarrativeTextBlock contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">
            Interest Rate Changes.&#160;Interest rate increases can cause the price of a debt security to decrease.



            Issuer-Specific Changes.&#160;The value of an individual security or particular type of security can be more volatile than, and can perform differently
               from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security
               can cause the price of a security to decrease.



            Correlation to Index.&#160;The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund,
               transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions
               from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified
               and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.



            Passive Management Risk.&#160;The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities,
               regardless of the current or projected performance of the fund&#x92;s index or of the actual securities included in the index.
               This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund&#x92;s
               performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities
               or lessen the impact of a market decline or a decline in the value of one or more issuers.



            Leverage Risk.&#160;Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.



            Investing for Inflation Protection.&#160;Increases in real interest rates can cause the price of inflation-protected debt securities to decrease. Interest payments
               on inflation-protected debt securities can be unpredictable.


                  An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.  Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will
            fluctuate. You could lose money by investing in the fund.


</rr:RiskNarrativeTextBlock>
    <rr:RiskNotInsuredDepositoryInstitution contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.</rr:RiskNotInsuredDepositoryInstitution>
    <rr:RiskLoseMoney contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">You could lose money by investing in the fund.</rr:RiskLoseMoney>
    <rr:BarChartAndPerformanceTableHeading contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">         Performance

</rr:BarChartAndPerformanceTableHeading>
    <rr:PerformanceOneYearOrLess contextRef="S000072689_D1231FidelitySeries055YearInflationProtectedBondIndexFundsSeriesComboPRO02Member">Performance history will be available for the fund after the fund has been in operation for one calendar year.</rr:PerformanceOneYearOrLess>
    <rr:RiskReturnHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Fund Summary
                  Fund:Fidelity&#xae; Series Inflation-Protected Bond Index Fund

</rr:RiskReturnHeading>
    <rr:ObjectiveHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Investment Objective

</rr:ObjectiveHeading>
    <rr:ObjectivePrimaryTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         The fund seeks to provide investment results that correspond to the total return of the inflation-protected sector of the
            United States Treasury market.


</rr:ObjectivePrimaryTextBlock>
    <rr:ExpenseHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Fee Table

</rr:ExpenseHeading>
    <rr:ExpenseNarrativeTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

</rr:ExpenseNarrativeTextBlock>
    <rr:ShareholderFeesCaption contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Shareholder fees

</rr:ShareholderFeesCaption>
    <rr:ShareholderFeeOther
      contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="0"
      unitRef="usd">0</rr:ShareholderFeeOther>
    <rr:OperatingExpensesCaption contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Annual Operating Expenses
                  (expenses that you pay each year as a % of the value of your investment)

</rr:OperatingExpensesCaption>
    <rr:ManagementFeesOverAssets
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0</rr:ManagementFeesOverAssets>
    <rr:DistributionAndService12b1FeesOverAssets
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0</rr:DistributionAndService12b1FeesOverAssets>
    <rr:OtherExpensesOverAssets
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0000</rr:OtherExpensesOverAssets>
    <rr:ExpensesOverAssets
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0000</rr:ExpensesOverAssets>
    <rr:ExpenseExampleNarrativeTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         This example helps compare the cost of investing in the fund with the cost of investing in other funds.

                  Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual
            operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses
            or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end
            of each time period indicated:


</rr:ExpenseExampleNarrativeTextBlock>
    <rr:ExpenseExampleYear01
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear01>
    <rr:ExpenseExampleYear03
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear03>
    <rr:ExpenseExampleYear05
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear05>
    <rr:ExpenseExampleYear10
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="0"
      unitRef="usd">0</rr:ExpenseExampleYear10>
    <rr:PortfolioTurnoverHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Portfolio Turnover

</rr:PortfolioTurnoverHeading>
    <rr:PortfolioTurnoverTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are
            held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 29%  of the average value of its portfolio.


</rr:PortfolioTurnoverTextBlock>
    <rr:PortfolioTurnoverRate
      contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.29</rr:PortfolioTurnoverRate>
    <rr:StrategyHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Principal Investment Strategies

</rr:StrategyHeading>
    <rr:StrategyNarrativeTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
            Normally investing at least 80% of assets in inflation-protected debt securities included in the Bloomberg U.S. Treasury Inflation-Protected
               Securities (TIPS) 1-10 Year Index.



            Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest
               rate, total return, and credit default) and futures contracts - and forward-settling securities, to adjust the fund's risk
               exposure.



</rr:StrategyNarrativeTextBlock>
    <rr:RiskHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Principal Investment Risks

</rr:RiskHeading>
    <rr:RiskNarrativeTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">
            Interest Rate Changes.&#160;Interest rate increases can cause the price of a debt security to decrease.



            Prepayment.&#160;The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility
               if interest rates change.



            Issuer-Specific Changes.&#160;The value of an individual security or particular type of security can be more volatile than, and can perform differently
               from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security
               can cause the price of a security to decrease.



            Correlation to Index.&#160;The performance of the fund and its underlying index may vary somewhat due to factors such as fees and expenses of the fund,
               transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions
               from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified
               and corrected for some period of time, which may have an adverse impact on the fund and its shareholders.



            Passive Management Risk.&#160;The fund is managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities,
               regardless of the current or projected performance of the fund&#x92;s index or of the actual securities included in the index.
               This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the fund&#x92;s
               performance could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities
               or lessen the impact of a market decline or a decline in the value of one or more issuers.



            Leverage Risk.&#160;Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.



            Investing for Inflation Protection.&#160;Increases in real interest rates can cause the price of inflation-protected debt securities to decrease. Interest payments
               on inflation-protected debt securities can be unpredictable.


                  An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.  Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will
            fluctuate. You could lose money by investing in the fund.


</rr:RiskNarrativeTextBlock>
    <rr:RiskNotInsuredDepositoryInstitution contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation
               or any other government agency.</rr:RiskNotInsuredDepositoryInstitution>
    <rr:RiskLoseMoney contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">You could lose money by investing in the fund.</rr:RiskLoseMoney>
    <rr:BarChartAndPerformanceTableHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Performance

</rr:BarChartAndPerformanceTableHeading>
    <rr:PerformanceNarrativeTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">                  The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.  The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

                  Visit www.fidelity.com  for more recent performance information.


</rr:PerformanceNarrativeTextBlock>
    <rr:PerformanceInformationIllustratesVariabilityOfReturns contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance
               of the fund's shares to the performance of a securities market index over various periods of time.</rr:PerformanceInformationIllustratesVariabilityOfReturns>
    <rr:PerformancePastDoesNotIndicateFuture contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Past performance (before and after taxes) is not an indication of future performance.</rr:PerformancePastDoesNotIndicateFuture>
    <rr:PerformanceAvailabilityWebSiteAddress contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">www.fidelity.com</rr:PerformanceAvailabilityWebSiteAddress>
    <rr:BarChartHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         Year-by-Year Returns

</rr:BarChartHeading>
    <rr:HighestQuarterlyReturnLabel contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Highest Quarter Return</rr:HighestQuarterlyReturnLabel>
    <rr:BarChartHighestQuarterlyReturn
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0373</rr:BarChartHighestQuarterlyReturn>
    <rr:BarChartHighestQuarterlyReturnDate contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">2020-06-30</rr:BarChartHighestQuarterlyReturnDate>
    <rr:LowestQuarterlyReturnLabel contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Lowest Quarter Return</rr:LowestQuarterlyReturnLabel>
    <rr:BarChartLowestQuarterlyReturn
      contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">-0.0562</rr:BarChartLowestQuarterlyReturn>
    <rr:BarChartLowestQuarterlyReturnDate contextRef="S000026423_C000079293_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">2013-06-30</rr:BarChartLowestQuarterlyReturnDate>
    <rr:PerformanceTableHeading contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Average Annual Returns

</rr:PerformanceTableHeading>
    <rr:PerformanceTableNarrativeTextBlock contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">         After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.  Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).  Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.


</rr:PerformanceTableNarrativeTextBlock>
    <rr:PerformanceTableUsesHighestFederalRate contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect
               the impact of state or local taxes.</rr:PerformanceTableUsesHighestFederalRate>
    <rr:PerformanceTableNotRelevantToTaxDeferred contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement,
               such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).</rr:PerformanceTableNotRelevantToTaxDeferred>
    <rr:PerformanceTableExplanationAfterTaxHigher contextRef="S000026423_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a
               tax benefit of realizing a capital loss upon the sale of fund shares.</rr:PerformanceTableExplanationAfterTaxHigher>
    <rr:AverageAnnualReturnLabel contextRef="S000026423_C000079293_ReturnBeforeTaxes_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Return Before Taxes</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000026423_C000079293_ReturnBeforeTaxes_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0560</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000026423_C000079293_ReturnBeforeTaxes_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0441</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnYear10
      contextRef="S000026423_C000079293_ReturnBeforeTaxes_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0243</rr:AverageAnnualReturnYear10>
    <rr:AverageAnnualReturnLabel contextRef="S000026423_C000079293_AfterTaxesOnDistributions_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Return After Taxes on Distributions</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000026423_C000079293_AfterTaxesOnDistributions_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0275</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000026423_C000079293_AfterTaxesOnDistributions_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0327</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnYear10
      contextRef="S000026423_C000079293_AfterTaxesOnDistributions_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0129</rr:AverageAnnualReturnYear10>
    <rr:AverageAnnualReturnLabel contextRef="S000026423_C000079293_AfterTaxesOnDistributionsAndSales_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Return After Taxes on Distributions and Sale of Fund Shares</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000026423_C000079293_AfterTaxesOnDistributionsAndSales_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0330</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000026423_C000079293_AfterTaxesOnDistributionsAndSales_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0290</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnYear10
      contextRef="S000026423_C000079293_AfterTaxesOnDistributionsAndSales_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0137</rr:AverageAnnualReturnYear10>
    <rr:AverageAnnualReturnLabel contextRef="S000026423_IndexLB200_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member">Bloomberg U.S. Treasury Inflation-Protected Securities (TIPS) 1-10 Year Index</rr:AverageAnnualReturnLabel>
    <rr:AverageAnnualReturnYear01
      contextRef="S000026423_IndexLB200_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0569</rr:AverageAnnualReturnYear01>
    <rr:AverageAnnualReturnYear05
      contextRef="S000026423_IndexLB200_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0446</rr:AverageAnnualReturnYear05>
    <rr:AverageAnnualReturnYear10
      contextRef="S000026423_IndexLB200_D1231FidelitySeriesInflationProtectedBondIndexFundSeriesPRO10Member"
      decimals="4"
      unitRef="pure">0.0257</rr:AverageAnnualReturnYear10>
    <link:footnoteLink
      xlink:role="http://www.xbrl.org/2003/role/link"
      xlink:type="extended">
        <link:loc
          xlink:href="#id_footnote_elem_778888579_7"
          xlink:label="id_footnote_elem_778888579_7"
          xlink:type="locator"/>
        <link:footnote id="footnote_775469274" xlink:label="footnote_775469274" xlink:role="http://www.xbrl.org/2003/role/footnote" xlink:type="resource" xml:lang="en-US"><xhtml:p style="font: 11px Arial, Helvetica, sans-serif;"><xhtml:sup>(a)</xhtml:sup><xhtml:i>The fund is available only to certain fee-based accounts and advisory programs offered by Fidelity. Advisory account clients,
               retirement plans, plan sponsors and/or plan participants typically pay an advisory fee that generally covers investment advisory
               and administrative services.</xhtml:i></xhtml:p>

</link:footnote>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_778888579_7"
          xlink:to="footnote_775469274"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_778888887_40"
          xlink:label="id_footnote_elem_778888887_40"
          xlink:type="locator"/>
        <link:footnote id="footnote_634225628" xlink:label="footnote_634225628" xlink:role="http://www.xbrl.org/2003/role/footnote" xlink:type="resource" xml:lang="en-US"><xhtml:p style="font: 11px Arial, Helvetica, sans-serif;"><xhtml:sup>(a)</xhtml:sup><xhtml:i>From March 9, 2017 </xhtml:i></xhtml:p>

</link:footnote>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_778888887_40"
          xlink:to="footnote_634225628"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_778888887_43"
          xlink:label="id_footnote_elem_778888887_43"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_778888887_43"
          xlink:to="footnote_634225628"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_778888887_46"
          xlink:label="id_footnote_elem_778888887_46"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_778888887_46"
          xlink:to="footnote_634225628"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_778888887_49"
          xlink:label="id_footnote_elem_778888887_49"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_778888887_49"
          xlink:to="footnote_634225628"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780049143_95"
          xlink:label="id_footnote_elem_780049143_95"
          xlink:type="locator"/>
        <link:footnote id="footnote_666887236" xlink:label="footnote_666887236" xlink:role="http://www.xbrl.org/2003/role/footnote" xlink:type="resource" xml:lang="en-US"><xhtml:p style="font: 11px Arial, Helvetica, sans-serif;"><xhtml:sup>(a)</xhtml:sup><xhtml:i>From May 16, 2012 </xhtml:i></xhtml:p>

</link:footnote>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780049143_95"
          xlink:to="footnote_666887236"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780049143_99"
          xlink:label="id_footnote_elem_780049143_99"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780049143_99"
          xlink:to="footnote_666887236"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780049143_103"
          xlink:label="id_footnote_elem_780049143_103"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780049143_103"
          xlink:to="footnote_666887236"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780049143_107"
          xlink:label="id_footnote_elem_780049143_107"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780049143_107"
          xlink:to="footnote_666887236"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780042260_146"
          xlink:label="id_footnote_elem_780042260_146"
          xlink:type="locator"/>
        <link:footnote id="footnote_668268102" xlink:label="footnote_668268102" xlink:role="http://www.xbrl.org/2003/role/footnote" xlink:type="resource" xml:lang="en-US"><xhtml:p style="font: 11px Arial, Helvetica, sans-serif;"><xhtml:sup>(a)</xhtml:sup><xhtml:i>From October 10, 2019 </xhtml:i></xhtml:p>

</link:footnote>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780042260_146"
          xlink:to="footnote_668268102"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780042260_149"
          xlink:label="id_footnote_elem_780042260_149"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780042260_149"
          xlink:to="footnote_668268102"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780042260_152"
          xlink:label="id_footnote_elem_780042260_152"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780042260_152"
          xlink:to="footnote_668268102"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780042260_155"
          xlink:label="id_footnote_elem_780042260_155"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780042260_155"
          xlink:to="footnote_668268102"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_779401293_193"
          xlink:label="id_footnote_elem_779401293_193"
          xlink:type="locator"/>
        <link:footnote id="footnote_634262720" xlink:label="footnote_634262720" xlink:role="http://www.xbrl.org/2003/role/footnote" xlink:type="resource" xml:lang="en-US"><xhtml:p style="font: 11px Arial, Helvetica, sans-serif;"><xhtml:sup>(a)</xhtml:sup><xhtml:i>From October 2, 2018 </xhtml:i></xhtml:p>

</link:footnote>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_779401293_193"
          xlink:to="footnote_634262720"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_779401293_196"
          xlink:label="id_footnote_elem_779401293_196"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_779401293_196"
          xlink:to="footnote_634262720"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_779401293_199"
          xlink:label="id_footnote_elem_779401293_199"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_779401293_199"
          xlink:to="footnote_634262720"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_779401293_202"
          xlink:label="id_footnote_elem_779401293_202"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_779401293_202"
          xlink:to="footnote_634262720"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_779401293_205"
          xlink:label="id_footnote_elem_779401293_205"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_779401293_205"
          xlink:to="footnote_634262720"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780494553_212"
          xlink:label="id_footnote_elem_780494553_212"
          xlink:type="locator"/>
        <link:footnote id="footnote_777506087" xlink:label="footnote_777506087" xlink:role="http://www.xbrl.org/2003/role/footnote" xlink:type="resource" xml:lang="en-US"><xhtml:p style="font: 11px Arial, Helvetica, sans-serif;"><xhtml:sup>(a)</xhtml:sup><xhtml:i>Based on estimated amounts for the current fiscal year. </xhtml:i></xhtml:p>

</link:footnote>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780494553_212"
          xlink:to="footnote_777506087"
          xlink:type="arc"/>
        <link:loc
          xlink:href="#id_footnote_elem_780494925_230"
          xlink:label="id_footnote_elem_780494925_230"
          xlink:type="locator"/>
        <link:footnoteArc
          xlink:arcrole="http://www.xbrl.org/2003/arcrole/fact-footnote"
          xlink:from="id_footnote_elem_780494925_230"
          xlink:to="footnote_777506087"
          xlink:type="arc"/>
    </link:footnoteLink>
</xbrl>
