<?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="olma-20260428.xsd" xlink:type="simple"/>
    <context id="C_f066ff2a-dcbb-4db3-9088-fa424ee78d8f">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001750284</identifier>
        </entity>
        <period>
            <startDate>2025-01-01</startDate>
            <endDate>2025-12-31</endDate>
        </period>
    </context>
    <dei:AmendmentFlag
      contextRef="C_f066ff2a-dcbb-4db3-9088-fa424ee78d8f"
      id="F_842b9908-768d-4299-91e8-aa2808d31e8d">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="C_f066ff2a-dcbb-4db3-9088-fa424ee78d8f"
      id="F_29b07d6d-c87b-49ba-aed3-3bc52421a106">0001750284</dei:EntityCentralIndexKey>
    <dei:DocumentType
      contextRef="C_f066ff2a-dcbb-4db3-9088-fa424ee78d8f"
      id="F_a4c29b57-59c0-491c-a552-c4ecb4ff04b8">DEFA14A</dei:DocumentType>
    <dei:EntityRegistrantName
      contextRef="C_f066ff2a-dcbb-4db3-9088-fa424ee78d8f"
      id="F_01dcde59-50b8-4cfd-89b0-7339e3cc6b04">Olema Pharmaceuticals, Inc.</dei:EntityRegistrantName>
</xbrl>