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<xbrl
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  xmlns:dei="http://xbrl.sec.gov/dei/2025"
  xmlns:imcr="http://immunocore.com./20260225"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:us-gaap="http://fasb.org/us-gaap/2025"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="imcr-20260225.xsd" xlink:type="simple"/>
    <context id="c20260225to20260225">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001671927</identifier>
        </entity>
        <period>
            <startDate>2026-02-25</startDate>
            <endDate>2026-02-25</endDate>
        </period>
    </context>
    <context id="c20260225to20260225_StatementClassOfStockAxis_OrdinaryShareNominalValue0002PerShareMember">
        <entity>
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            <segment>
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        </entity>
        <period>
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            <endDate>2026-02-25</endDate>
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    </context>
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        <entity>
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            <segment>
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        <period>
            <startDate>2026-02-25</startDate>
            <endDate>2026-02-25</endDate>
        </period>
    </context>
    <dei:AmendmentFlag
      contextRef="c20260225to20260225"
      id="Fact_250538e4e821412e857745bc004b128e">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="c20260225to20260225"
      id="Fact_aaa86321ccf34829809414b68f47ebe3">0001671927</dei:EntityCentralIndexKey>
    <dei:EntityIncorporationStateCountryCode
      contextRef="c20260225to20260225"
      id="Fact_86c07db62f8542e7b5266aa6f5508736">X0</dei:EntityIncorporationStateCountryCode>
    <dei:EntityTaxIdentificationNumber
      contextRef="c20260225to20260225"
      id="Fact_7179d905fcd44be2b3fd3063d7f063d1">00-0000000</dei:EntityTaxIdentificationNumber>
    <dei:Security12bTitle
      contextRef="c20260225to20260225_StatementClassOfStockAxis_OrdinaryShareNominalValue0002PerShareMember"
      id="Fact_c7bfe0d81bf84bf5a97521cc0706e5c2">Ordinary share, nominal value 0.002 per share*</dei:Security12bTitle>
    <dei:Security12bTitle
      contextRef="c20260225to20260225_StatementClassOfStockAxis_AmericanDepositarySharesEachRepresentingOneOrdinaryShareNominalValue0002PerShareMember"
      id="Fact_0dd69d95358a451387bd6a571bd44601">American Depositary Shares, each representing one ordinary share, nominal value 0.002 per share</dei:Security12bTitle>
    <dei:SecurityExchangeName
      contextRef="c20260225to20260225_StatementClassOfStockAxis_AmericanDepositarySharesEachRepresentingOneOrdinaryShareNominalValue0002PerShareMember"
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      contextRef="c20260225to20260225_StatementClassOfStockAxis_OrdinaryShareNominalValue0002PerShareMember"
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      contextRef="c20260225to20260225"
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      contextRef="c20260225to20260225"
      id="Fact_f302ce8a6b1c4c3997c4675c23c8e08b">2026-02-25</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="c20260225to20260225"
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    <dei:EntityFileNumber
      contextRef="c20260225to20260225"
      id="Fact_d788b2009e2d4a44bf2c87af794fd482">001-39992</dei:EntityFileNumber>
    <dei:EntityAddressAddressLine1
      contextRef="c20260225to20260225"
      id="Fact_d5a72c77266746dab47419523eb1df5c">92 Park Drive</dei:EntityAddressAddressLine1>
    <dei:EntityAddressAddressLine2
      contextRef="c20260225to20260225"
      id="Fact_53ca2562655b41c1ad778b400382b2d9">Milton Park Abingdon</dei:EntityAddressAddressLine2>
    <dei:EntityAddressCityOrTown
      contextRef="c20260225to20260225"
      id="Fact_d2b5b2226fda4b339e97303895c86c7e">Oxfordshire</dei:EntityAddressCityOrTown>
    <dei:EntityAddressCountry
      contextRef="c20260225to20260225"
      id="Fact_8d3af2bb6356495c9cc65a6dbe8d6bb4">GB</dei:EntityAddressCountry>
    <dei:EntityAddressPostalZipCode
      contextRef="c20260225to20260225"
      id="Fact_bb8c106e83c849a3887c88dd687313ca">OX14 4RY</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="c20260225to20260225"
      id="Fact_ce298ce5ed4e435cbaea2c44a8c9a761">44</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="c20260225to20260225"
      id="Fact_18f38d71fc25434d951736506b997daf">1235 438600</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="c20260225to20260225"
      id="Fact_a90f31d7a32e4b719ed00dd335e70382">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="c20260225to20260225"
      id="Fact_1c28b9b01f6846228baffa5c5167350a">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="c20260225to20260225"
      id="Fact_becc57570dc24a858fb71d0f72e68a95">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="c20260225to20260225"
      id="Fact_2cbe863c27904828917a5ab056f8f822">false</dei:PreCommencementIssuerTenderOffer>
    <dei:TradingSymbol
      contextRef="c20260225to20260225_StatementClassOfStockAxis_AmericanDepositarySharesEachRepresentingOneOrdinaryShareNominalValue0002PerShareMember"
      id="Fact_a9217c04979844f284d18665a6b3393e">IMCR</dei:TradingSymbol>
    <dei:TradingSymbol
      contextRef="c20260225to20260225_StatementClassOfStockAxis_OrdinaryShareNominalValue0002PerShareMember"
      id="Fact_433ceee7fb7d4e898fcd3dd8e70b2c40">*</dei:TradingSymbol>
    <dei:EntityEmergingGrowthCompany
      contextRef="c20260225to20260225"
      id="Fact_cd6b97acb2964620807e60199338d126">false</dei:EntityEmergingGrowthCompany>
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