<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2023"
  xmlns:fmr="http://www.fidelity.com/20240928"
  xmlns:iso4217="http://www.xbrl.org/2003/iso4217"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:oef="http://xbrl.sec.gov/oef/2023"
  xmlns:us-gaap="http://fasb.org/us-gaap/2023"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="fmr-20240928.xsd" xlink:type="simple"/>
    <context id="C000047913_ClassMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-01-31</startDate>
            <endDate>2024-07-31</endDate>
        </period>
    </context>
    <context id="C000047913_InstantMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_EMD_0_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD0Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_EMD_1_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD1Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_EMD_2_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD2Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_EMD_3_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD3Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_EMD_4_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD4Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_EMD_5_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD5Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_AA_VariableRateDemandNotesVRDNs_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AAVariableRateDemandNotesVRDNsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_AA_MunicipalSecurities_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AAMunicipalSecuritiesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_AA_TenderOptionBond_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AATenderOptionBondMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_AA_CommercialPaper_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AACommercialPaperMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000047913_AA_NetOtherAssetsLiabilities_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AANetOtherAssetsLiabilitiesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000047913Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_ClassMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-01-31</startDate>
            <endDate>2024-07-31</endDate>
        </period>
    </context>
    <context id="C000019443_InstantMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_RS_0_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:OtherCategory1Axis">fmr:RS0Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_RS_1_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:OtherCategory1Axis">fmr:RS1Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_RS_2_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:OtherCategory1Axis">fmr:RS2Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_RS_3_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:OtherCategory1Axis">fmr:RS3Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_RS_4_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:OtherCategory1Axis">fmr:RS4Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_RS_5_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:OtherCategory1Axis">fmr:RS5Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_AAA_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDAAAMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_AA_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDAAMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_A_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDAMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_BBB_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDBBBMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_BB_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDBBMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_B_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDBMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_NotRated_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDNotRatedMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019443_QD_ShortTermInvestmentsandNetOtherAssetsLiabilities_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019443Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:CreditQualityAxis">fmr:QDShortTermInvestmentsandNetOtherAssetsLiabilitiesMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_ClassMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-01-31</startDate>
            <endDate>2024-07-31</endDate>
        </period>
    </context>
    <context id="C000238262_InstantMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_EMD_0_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD0Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_EMD_1_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD1Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_EMD_2_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD2Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_EMD_3_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD3Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_EMD_4_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD4Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_EMD_5_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD5Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_AA_VariableRateDemandNotesVRDNs_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AAVariableRateDemandNotesVRDNsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_AA_MunicipalSecurities_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AAMunicipalSecuritiesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_AA_TenderOptionBond_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AATenderOptionBondMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_AA_CommercialPaper_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AACommercialPaperMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000238262_AA_NetOtherAssetsLiabilities_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AANetOtherAssetsLiabilitiesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000238262Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_ClassMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2024-01-31</startDate>
            <endDate>2024-07-31</endDate>
        </period>
    </context>
    <context id="C000019442_InstantMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_EMD_0_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD0Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_EMD_1_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD1Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_EMD_2_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD2Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_EMD_3_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD3Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_EMD_4_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD4Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_EMD_5_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:MaturityAxis">fmr:EMD5Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_AA_VariableRateDemandNotesVRDNs_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AAVariableRateDemandNotesVRDNsMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_AA_MunicipalSecurities_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AAMunicipalSecuritiesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_AA_TenderOptionBond_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AATenderOptionBondMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_AA_CommercialPaper_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AACommercialPaperMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="C000019442_AA_NetOtherAssetsLiabilities_Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:InvestmentTypeAxis">fmr:AANetOtherAssetsLiabilitiesMember</xbrldi:explicitMember>
                <xbrldi:explicitMember dimension="oef:ClassAxis">fmr:C000019442Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <instant>2024-07-31</instant>
        </period>
    </context>
    <context id="Trust">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000357057</identifier>
        </entity>
        <period>
            <startDate>2024-01-31</startDate>
            <endDate>2024-07-31</endDate>
        </period>
    </context>
    <unit id="usd">
        <measure>iso4217:USD</measure>
    </unit>
    <unit id="pure">
        <measure>pure</measure>
    </unit>
    <unit id="holding">
        <measure>shares</measure>
    </unit>
    <dei:DocumentType contextRef="Trust" id="ixv-24272">N-CSRS</dei:DocumentType>
    <dei:AmendmentFlag contextRef="Trust" id="ixv-24273">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey contextRef="Trust" id="ixv-24274">0000357057</dei:EntityCentralIndexKey>
    <dei:EntityInvCompanyType contextRef="Trust" id="ixv-24275">N-1A</dei:EntityInvCompanyType>
    <dei:EntityRegistrantName contextRef="Trust" id="ixv-24276">Fidelity Massachusetts Municipal Trust</dei:EntityRegistrantName>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-95">2024-07-31</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000047913_ClassMember" id="ixv-107">Fidelity&#xae; Massachusetts Municipal Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000047913_ClassMember" id="ixv-110">Fidelity&#xae; Massachusetts Municipal Money Market Fund Institutional Class</oef:ClassName>
    <dei:TradingSymbol contextRef="C000047913_ClassMember" id="ixv-114">FMAXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000047913_ClassMember" id="ixv-134">This semi-annual shareholder report contains information about Fidelity&#xae; Massachusetts Municipal Money Market Fund for the period February 1, 2024 to July 31, 2024.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000047913_ClassMember" id="ixv-136">semi-annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000047913_ClassMember" id="ixv-141">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-877-208-0098 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000047913_ClassMember" id="ixv-143">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000047913_ClassMember" id="ixv-146">1-877-208-0098</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000047913_ClassMember" id="ixv-149">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000047913_ClassMember" id="ixv-156">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last six months?&lt;/span&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:43%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:43%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Institutional Class&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;10&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;0.20&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000047913_ClassMember"
      decimals="0"
      id="ixv-24728"
      unitRef="usd">10</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000047913_ClassMember"
      decimals="INF"
      id="ixv-24729"
      unitRef="pure">0.0020</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000047913_ClassMember" id="ixv-197">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;span style="line-height:16px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of July 31, 2024)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;3,025,435,985&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;268&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000047913_InstantMember"
      decimals="0"
      id="ixv-24730"
      unitRef="usd">3025435985</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000047913_InstantMember"
      decimals="INF"
      id="ixv-24731"
      unitRef="holding">268</oef:HoldingsCount>
    <oef:HoldingsTableTextBlock contextRef="C000047913_ClassMember" id="ixv-248">
&#160;

EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

71.6

&#160;


8-30

2.4

&#160;


31-60

5.8

&#160;


61-90

5.7

&#160;


91-180

6.3

&#160;


&gt;180

7.2

&#160;


&#160;
&#160;




&#160;

Variable Rate Demand Notes (VRDNs)

33.9


Municipal Securities

28.2


Tender Option Bond

23.7


Commercial Paper

0.3


Net Other Assets (Liabilities)

13.9




ASSET ALLOCATION (% of Fund's net assets)









</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000047913_EMD_0_Member"
      decimals="INF"
      id="ixv-24732"
      unitRef="pure">0.716</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_EMD_1_Member"
      decimals="INF"
      id="ixv-24733"
      unitRef="pure">0.024</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_EMD_2_Member"
      decimals="INF"
      id="ixv-24734"
      unitRef="pure">0.058</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_EMD_3_Member"
      decimals="INF"
      id="ixv-24735"
      unitRef="pure">0.057</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_EMD_4_Member"
      decimals="INF"
      id="ixv-24736"
      unitRef="pure">0.063</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_EMD_5_Member"
      decimals="INF"
      id="ixv-24737"
      unitRef="pure">0.072</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_AA_VariableRateDemandNotesVRDNs_Member"
      decimals="INF"
      id="ixv-24738"
      unitRef="pure">0.339</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_AA_MunicipalSecurities_Member"
      decimals="INF"
      id="ixv-24739"
      unitRef="pure">0.282</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_AA_TenderOptionBond_Member"
      decimals="INF"
      id="ixv-24740"
      unitRef="pure">0.237</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_AA_CommercialPaper_Member"
      decimals="INF"
      id="ixv-24741"
      unitRef="pure">0.003</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000047913_AA_NetOtherAssetsLiabilities_Member"
      decimals="INF"
      id="ixv-24742"
      unitRef="pure">0.139</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-428">2024-07-31</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000019443_ClassMember" id="ixv-440">Fidelity&#xae; Massachusetts Municipal Income Fund</oef:FundName>
    <oef:ClassName contextRef="C000019443_ClassMember" id="ixv-443">Fidelity&#xae; Massachusetts Municipal Income Fund</oef:ClassName>
    <dei:TradingSymbol contextRef="C000019443_ClassMember" id="ixv-447">FDMMX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000019443_ClassMember" id="ixv-467">This semi-annual shareholder report contains information about Fidelity&#xae; Massachusetts Municipal Income Fund for the period February 1, 2024 to July 31, 2024.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000019443_ClassMember" id="ixv-469">semi-annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000019443_ClassMember" id="ixv-474">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000019443_ClassMember" id="ixv-476">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000019443_ClassMember" id="ixv-479">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000019443_ClassMember" id="ixv-482">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000019443_ClassMember" id="ixv-489">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last six months?&lt;/span&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:43%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:43%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity&#xae; Massachusetts Municipal Income Fund&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;23&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;0.45&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000019443_ClassMember"
      decimals="0"
      id="ixv-24743"
      unitRef="usd">23</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000019443_ClassMember"
      decimals="INF"
      id="ixv-24744"
      unitRef="pure">0.0045</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000019443_ClassMember" id="ixv-530">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;span style="line-height:16px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of July 31, 2024)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;1,722,695,148&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;465&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Portfolio Turnover&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;6&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000019443_InstantMember"
      decimals="0"
      id="ixv-24745"
      unitRef="usd">1722695148</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000019443_InstantMember"
      decimals="INF"
      id="ixv-24746"
      unitRef="holding">465</oef:HoldingsCount>
    <us-gaap:InvestmentCompanyPortfolioTurnover
      contextRef="C000019443_ClassMember"
      decimals="INF"
      id="ixv-24747"
      unitRef="pure">0.06</us-gaap:InvestmentCompanyPortfolioTurnover>
    <oef:HoldingsTableTextBlock contextRef="C000019443_ClassMember" id="ixv-593">
&#160;

REVENUE SOURCES
 (% of Fund's net assets)


General Obligations

22.5

&#160;


Education

21.9

&#160;


Health Care

17.7

&#160;


Transportation

13.0

&#160;


Special Tax

12.7

&#160;


Others(Individually Less Than 5%)

12.2

&#160;


100.0

&#160;


&#160;




&#160;

AAA

3.9


AA

62.0


A

10.8


BBB

16.7


BB

0.4


B

1.1


Not Rated

2.8


Short-Term Investments and Net Other Assets (Liabilities)

2.3




QUALITY DIVERSIFICATION (% of Fund's net assets)


&#160;


&#160;


We have used ratings from Moody's Investors Service, Inc. Where Moody's&#xae; ratings are not available, we have used S&amp;P&#xae; ratings. All ratings are as of the date indicated and do not reflect subsequent changes.




&#160;
&#160;
</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000019443_RS_0_Member"
      decimals="INF"
      id="ixv-24748"
      unitRef="pure">0.225</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_RS_1_Member"
      decimals="INF"
      id="ixv-24749"
      unitRef="pure">0.219</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_RS_2_Member"
      decimals="INF"
      id="ixv-24750"
      unitRef="pure">0.177</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_RS_3_Member"
      decimals="INF"
      id="ixv-24751"
      unitRef="pure">0.130</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_RS_4_Member"
      decimals="INF"
      id="ixv-24752"
      unitRef="pure">0.127</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_RS_5_Member"
      decimals="INF"
      id="ixv-24753"
      unitRef="pure">0.122</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_AAA_Member"
      decimals="INF"
      id="ixv-24754"
      unitRef="pure">0.039</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_AA_Member"
      decimals="INF"
      id="ixv-24755"
      unitRef="pure">0.620</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_A_Member"
      decimals="INF"
      id="ixv-24756"
      unitRef="pure">0.108</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_BBB_Member"
      decimals="INF"
      id="ixv-24757"
      unitRef="pure">0.167</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_BB_Member"
      decimals="INF"
      id="ixv-24758"
      unitRef="pure">0.004</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_B_Member"
      decimals="INF"
      id="ixv-24759"
      unitRef="pure">0.011</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_NotRated_Member"
      decimals="INF"
      id="ixv-24760"
      unitRef="pure">0.028</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019443_QD_ShortTermInvestmentsandNetOtherAssetsLiabilities_Member"
      decimals="INF"
      id="ixv-24761"
      unitRef="pure">0.023</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-800">2024-07-31</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000238262_ClassMember" id="ixv-812">Fidelity&#xae; Massachusetts Municipal Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000238262_ClassMember" id="ixv-815">Fidelity&#xae; Massachusetts Municipal Money Market Fund</oef:ClassName>
    <dei:TradingSymbol contextRef="C000238262_ClassMember" id="ixv-819">FAUXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000238262_ClassMember" id="ixv-839">This semi-annual shareholder report contains information about Fidelity&#xae; Massachusetts Municipal Money Market Fund for the period February 1, 2024 to July 31, 2024.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000238262_ClassMember" id="ixv-841">semi-annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000238262_ClassMember" id="ixv-846">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000238262_ClassMember" id="ixv-848">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000238262_ClassMember" id="ixv-851">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000238262_ClassMember" id="ixv-854">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000238262_ClassMember" id="ixv-861">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last six months?&lt;/span&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:43%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:43%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fidelity&#xae; Massachusetts Municipal Money Market Fund&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;21&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;0.42&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000238262_ClassMember"
      decimals="0"
      id="ixv-24762"
      unitRef="usd">21</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000238262_ClassMember"
      decimals="INF"
      id="ixv-24763"
      unitRef="pure">0.0042</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000238262_ClassMember" id="ixv-902">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;span style="line-height:16px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of July 31, 2024)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;3,025,435,985&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;268&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000238262_InstantMember"
      decimals="0"
      id="ixv-24764"
      unitRef="usd">3025435985</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000238262_InstantMember"
      decimals="INF"
      id="ixv-24765"
      unitRef="holding">268</oef:HoldingsCount>
    <oef:HoldingsTableTextBlock contextRef="C000238262_ClassMember" id="ixv-953">
&#160;

EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

71.6

&#160;


8-30

2.4

&#160;


31-60

5.8

&#160;


61-90

5.7

&#160;


91-180

6.3

&#160;


&gt;180

7.2

&#160;


&#160;
&#160;




&#160;

Variable Rate Demand Notes (VRDNs)

33.9


Municipal Securities

28.2


Tender Option Bond

23.7


Commercial Paper

0.3


Net Other Assets (Liabilities)

13.9




ASSET ALLOCATION (% of Fund's net assets)









</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000238262_EMD_0_Member"
      decimals="INF"
      id="ixv-24766"
      unitRef="pure">0.716</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_EMD_1_Member"
      decimals="INF"
      id="ixv-24767"
      unitRef="pure">0.024</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_EMD_2_Member"
      decimals="INF"
      id="ixv-24768"
      unitRef="pure">0.058</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_EMD_3_Member"
      decimals="INF"
      id="ixv-24769"
      unitRef="pure">0.057</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_EMD_4_Member"
      decimals="INF"
      id="ixv-24770"
      unitRef="pure">0.063</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_EMD_5_Member"
      decimals="INF"
      id="ixv-24771"
      unitRef="pure">0.072</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_AA_VariableRateDemandNotesVRDNs_Member"
      decimals="INF"
      id="ixv-24772"
      unitRef="pure">0.339</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_AA_MunicipalSecurities_Member"
      decimals="INF"
      id="ixv-24773"
      unitRef="pure">0.282</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_AA_TenderOptionBond_Member"
      decimals="INF"
      id="ixv-24774"
      unitRef="pure">0.237</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_AA_CommercialPaper_Member"
      decimals="INF"
      id="ixv-24775"
      unitRef="pure">0.003</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000238262_AA_NetOtherAssetsLiabilities_Member"
      decimals="INF"
      id="ixv-24776"
      unitRef="pure">0.139</oef:PctOfNav>
    <dei:DocumentPeriodEndDate contextRef="Trust" id="ixv-1133">2024-07-31</dei:DocumentPeriodEndDate>
    <oef:FundName contextRef="C000019442_ClassMember" id="ixv-1145">Fidelity&#xae; Massachusetts Municipal Money Market Fund</oef:FundName>
    <oef:ClassName contextRef="C000019442_ClassMember" id="ixv-1148">Fidelity&#xae; Massachusetts Municipal Money Market Fund Premium Class</oef:ClassName>
    <dei:TradingSymbol contextRef="C000019442_ClassMember" id="ixv-1152">FMSXX</dei:TradingSymbol>
    <oef:AnnlOrSemiAnnlStatementTextBlock contextRef="C000019442_ClassMember" id="ixv-1172">This semi-annual shareholder report contains information about Fidelity&#xae; Massachusetts Municipal Money Market Fund for the period February 1, 2024 to July 31, 2024.</oef:AnnlOrSemiAnnlStatementTextBlock>
    <oef:ShareholderReportAnnualOrSemiAnnual contextRef="C000019442_ClassMember" id="ixv-1174">semi-annual shareholder report</oef:ShareholderReportAnnualOrSemiAnnual>
    <oef:AddlInfoTextBlock contextRef="C000019442_ClassMember" id="ixv-1179">You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com.</oef:AddlInfoTextBlock>
    <oef:AddlInfoWebsite contextRef="C000019442_ClassMember" id="ixv-1181">fundresearch.fidelity.com/prospectus/sec</oef:AddlInfoWebsite>
    <oef:AddlInfoPhoneNumber contextRef="C000019442_ClassMember" id="ixv-1184">1-800-544-8544</oef:AddlInfoPhoneNumber>
    <oef:AddlInfoEmail contextRef="C000019442_ClassMember" id="ixv-1187">fidfunddocuments@fidelity.com</oef:AddlInfoEmail>
    <oef:ExpensesTextBlock contextRef="C000019442_ClassMember" id="ixv-1194">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;What were your Fund costs for the last six months?&lt;/span&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(based on hypothetical $10,000 investment)&lt;/span&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="0" style="border-collapse:collapse;border-style:none;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:43%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs of a $10,000 investment&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; background-color:#dfe0e4;border:1px solid #dfe0e4;padding:0px 0px 0px 0px;" valign="bottom"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;Costs paid as a percentage of a $10,000 investment &lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:43%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Premium Class&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:25%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$ &lt;/span&gt;15&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:31%; border-bottom:1px solid #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:center;"&gt;0.30&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;%&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:1%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:ExpensesTextBlock>
    <oef:ExpensesPaidAmt
      contextRef="C000019442_ClassMember"
      decimals="0"
      id="ixv-24777"
      unitRef="usd">15</oef:ExpensesPaidAmt>
    <oef:ExpenseRatioPct
      contextRef="C000019442_ClassMember"
      decimals="INF"
      id="ixv-24778"
      unitRef="pure">0.0030</oef:ExpenseRatioPct>
    <oef:AddlFundStatisticsTextBlock contextRef="C000019442_ClassMember" id="ixv-1235">&lt;span style="font-family:'Fidelity Sans';font-size:16px;color:#368627;font-style:normal;font-weight:bold;"&gt;Key Fund Statistics&lt;/span&gt;
&lt;span style="line-height:16px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;(as of July 31, 2024)&lt;/span&gt;&lt;/div&gt;
&lt;div&gt;&lt;span style="font-size:11px;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;table cellpadding="0" cellspacing="1" style="border-collapse:separate;border-style:none;margin:auto;" width="100%"&gt;&lt;tr&gt;&lt;td style="width:63%; " valign="top"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:12px;color:#000000;font-style:normal;font-weight:bold;"&gt;KEY FACTS&lt;/span&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;"&gt;&#160;&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:12px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Fund Size&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;$&lt;/span&gt;3,025,435,985&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;&lt;td style="width:63%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:left;"&gt;&lt;span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;"&gt;Number of Holdings&lt;/span&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:32%; border-bottom:1px dashed #000000;padding:0px 0px 0px 0px;" valign="middle"&gt;&lt;div style="text-align:right;"&gt;268&lt;/div&gt;
&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:right;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;td style="width:5%; " valign="top"&gt;&lt;span style="line-height:11px;"&gt;&#160;&lt;/span&gt;&lt;div style="text-align:left;"&gt;&lt;/div&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
&lt;div style="text-align:left;"&gt;&lt;/div&gt;</oef:AddlFundStatisticsTextBlock>
    <us-gaap:AssetsNet
      contextRef="C000019442_InstantMember"
      decimals="0"
      id="ixv-24779"
      unitRef="usd">3025435985</us-gaap:AssetsNet>
    <oef:HoldingsCount
      contextRef="C000019442_InstantMember"
      decimals="INF"
      id="ixv-24780"
      unitRef="holding">268</oef:HoldingsCount>
    <oef:HoldingsTableTextBlock contextRef="C000019442_ClassMember" id="ixv-1286">
&#160;

EFFECTIVE MATURITY DIVERSIFICATION
(% of Fund's net assets)


&#160;
Days
&#160;


1-7

71.6

&#160;


8-30

2.4

&#160;


31-60

5.8

&#160;


61-90

5.7

&#160;


91-180

6.3

&#160;


&gt;180

7.2

&#160;


&#160;
&#160;




&#160;

Variable Rate Demand Notes (VRDNs)

33.9


Municipal Securities

28.2


Tender Option Bond

23.7


Commercial Paper

0.3


Net Other Assets (Liabilities)

13.9




ASSET ALLOCATION (% of Fund's net assets)









</oef:HoldingsTableTextBlock>
    <oef:PctOfNav
      contextRef="C000019442_EMD_0_Member"
      decimals="INF"
      id="ixv-24781"
      unitRef="pure">0.716</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_EMD_1_Member"
      decimals="INF"
      id="ixv-24782"
      unitRef="pure">0.024</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_EMD_2_Member"
      decimals="INF"
      id="ixv-24783"
      unitRef="pure">0.058</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_EMD_3_Member"
      decimals="INF"
      id="ixv-24784"
      unitRef="pure">0.057</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_EMD_4_Member"
      decimals="INF"
      id="ixv-24785"
      unitRef="pure">0.063</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_EMD_5_Member"
      decimals="INF"
      id="ixv-24786"
      unitRef="pure">0.072</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_AA_VariableRateDemandNotesVRDNs_Member"
      decimals="INF"
      id="ixv-24787"
      unitRef="pure">0.339</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_AA_MunicipalSecurities_Member"
      decimals="INF"
      id="ixv-24788"
      unitRef="pure">0.282</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_AA_TenderOptionBond_Member"
      decimals="INF"
      id="ixv-24789"
      unitRef="pure">0.237</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_AA_CommercialPaper_Member"
      decimals="INF"
      id="ixv-24790"
      unitRef="pure">0.003</oef:PctOfNav>
    <oef:PctOfNav
      contextRef="C000019442_AA_NetOtherAssetsLiabilities_Member"
      decimals="INF"
      id="ixv-24791"
      unitRef="pure">0.139</oef:PctOfNav>
</xbrl>
