<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2025"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="bolt-20260427.xsd" xlink:type="simple"/>
    <context id="C_542e1a3d-f5f9-4c19-9d99-bed2bc7e1c26">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001641281</identifier>
        </entity>
        <period>
            <startDate>2025-01-01</startDate>
            <endDate>2025-12-31</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="C_542e1a3d-f5f9-4c19-9d99-bed2bc7e1c26"
      id="F_ce849285-e7e8-4b99-b426-221438603df7">0001641281</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="C_542e1a3d-f5f9-4c19-9d99-bed2bc7e1c26"
      id="F_e19762d8-64f5-40a9-9af0-c58794ba1e75">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="C_542e1a3d-f5f9-4c19-9d99-bed2bc7e1c26"
      id="F_717cfe0a-22ee-4b90-ade9-77c797a30c52">DEFA14A</dei:DocumentType>
    <dei:EntityRegistrantName
      contextRef="C_542e1a3d-f5f9-4c19-9d99-bed2bc7e1c26"
      id="F_48b93a3b-05ff-441c-a286-2a65d5b9f739">Bolt Biotherapeutics, Inc.</dei:EntityRegistrantName>
</xbrl>