<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2026"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:us-gaap="http://fasb.org/us-gaap/2026"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="mreo-20260811.xsd" xlink:type="simple"/>
    <context id="C_a3f53f2d-47af-4e11-9ebb-720727e8cf8e">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001719714</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">dei:AdrMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="C_6c9553ad-5183-4178-8eee-b85abb0e1250">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001719714</identifier>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="C_76e1f87f-2971-4b29-ba2f-8d0340d14456">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001719714</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:CommonStockMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <dei:NoTradingSymbolFlag
      contextRef="C_76e1f87f-2971-4b29-ba2f-8d0340d14456"
      id="F_a6f959bd-a879-4b54-9fc0-20c0947a7618">true</dei:NoTradingSymbolFlag>
    <dei:AmendmentFlag
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_8e008032-f8c4-4a3f-8cd4-a2c944cef8c5">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_88d9de6c-40e2-41ab-ae56-d57e3b40f421">0001719714</dei:EntityCentralIndexKey>
    <dei:EntityIncorporationStateCountryCode
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_86191ce9-f64d-416d-9c14-f76c6765cfda">X0</dei:EntityIncorporationStateCountryCode>
    <dei:EntityTaxIdentificationNumber
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_11e09d6c-eeba-4e8e-a4bd-979dfb19f897">00-0000000</dei:EntityTaxIdentificationNumber>
    <dei:DocumentType
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_3395afc4-b44f-4ec7-8ca3-be171e1cb00f">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_4d48f452-5211-43d4-b676-5db4f7e7cfb5">2026-08-11</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_9db215b0-f13e-4cf6-9670-c19a6ad1c6ed">MEREO BIOPHARMA GROUP PLC</dei:EntityRegistrantName>
    <dei:EntityFileNumber
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_79382fc2-d762-49ac-bc57-c3d9eedc2808">001-38452</dei:EntityFileNumber>
    <dei:EntityAddressAddressLine1
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_f81dff82-df88-403b-9eee-376675f2a6a2">4th Floor</dei:EntityAddressAddressLine1>
    <dei:EntityAddressAddressLine2
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_df50df88-58a3-42af-91d7-d9ba92a1e97a">One Cavendish Place</dei:EntityAddressAddressLine2>
    <dei:EntityAddressCityOrTown
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_594f9428-dd3e-4e35-b586-471ea865671f">London</dei:EntityAddressCityOrTown>
    <dei:EntityAddressPostalZipCode
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_0f02ee4b-f69d-40db-94e3-e8bcf5e02639">W1G 0QF</dei:EntityAddressPostalZipCode>
    <dei:EntityAddressCountry
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_ab3ced2f-7c83-4573-bcdc-3b781dea1238">GB</dei:EntityAddressCountry>
    <dei:CountryRegion
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_2f3b2229-636d-406d-88ff-fa9fcc09d324">44</dei:CountryRegion>
    <dei:CityAreaCode
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_8ebd3176-c4b3-4aae-9931-486139f6b009">333</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_12f267f6-9125-492c-acc0-d57f06fe1683">023-7300</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_5bb9d118-22ad-4fbf-b195-f99b7e37ace8">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_097ca22c-c046-4a99-932b-88757f0137e0">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_7b748e67-8675-42fc-8b50-aa6009692e25">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_89fbb7a4-0ee3-4e7b-b6d3-3b6fa22976b7">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="C_a3f53f2d-47af-4e11-9ebb-720727e8cf8e"
      id="F_935924c9-7a07-49c0-a579-243b48816144">American Depositary Shares, each representing five Ordinary Shares, par value &#xa3;0.003 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="C_a3f53f2d-47af-4e11-9ebb-720727e8cf8e"
      id="F_37c68ad1-3317-4b4b-9c51-ee7decb66ebf">MREO</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="C_a3f53f2d-47af-4e11-9ebb-720727e8cf8e"
      id="F_59676980-b2ed-4d38-a6c2-cfabd7e40f72">NASDAQ</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="C_76e1f87f-2971-4b29-ba2f-8d0340d14456"
      id="F_27701210-deb8-4f82-b67c-a97d0c2597d8">Ordinary Shares, nominal value &#xa3;0.003 per share</dei:Security12bTitle>
    <dei:SecurityExchangeName
      contextRef="C_76e1f87f-2971-4b29-ba2f-8d0340d14456"
      id="F_e62c70f8-adca-42aa-9f91-5025292ea395">NASDAQ</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="C_6c9553ad-5183-4178-8eee-b85abb0e1250"
      id="F_6d308582-032c-431e-b1af-6b16602f7583">false</dei:EntityEmergingGrowthCompany>
</xbrl>
