<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xml:lang="en-US"
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2021"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="anab-20210809.xsd" xlink:type="simple"/>
    <context id="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001370053</identifier>
        </entity>
        <period>
            <startDate>2021-08-09</startDate>
            <endDate>2021-08-09</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF80L2ZyYWc6M2Q1ZTgyZTMzZGZlNGEyYzhhM2E5MzdmODUxM2Q4YmIvdGFibGU6YjEwOTFlNjkxMjJjNDU1M2I5YWE1OGE3N2RjYzBhNjcvdGFibGVyYW5nZTpiMTA5MWU2OTEyMmM0NTUzYjlhYTU4YTc3ZGNjMGE2N18yLTEtMS0xLTA_59a20ac5-6821-4507-9b70-0cbc0139ec3b">0001370053</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF80L2ZyYWc6M2Q1ZTgyZTMzZGZlNGEyYzhhM2E5MzdmODUxM2Q4YmIvdGFibGU6YjEwOTFlNjkxMjJjNDU1M2I5YWE1OGE3N2RjYzBhNjcvdGFibGVyYW5nZTpiMTA5MWU2OTEyMmM0NTUzYjlhYTU4YTc3ZGNjMGE2N181LTEtMS0xLTA_5a8061fc-edd9-4c9e-8807-65486630f3f7">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzU4_ba760740-781e-4fd5-95e1-c25b9645d066">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xOTE_67abb02a-78ab-43eb-a0f0-dcdfd614072d">2021-08-09</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzY0_f3de3574-7f50-462e-a1f1-d9153b051f99">ANAPTYSBIO, INC</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGFibGU6YWUwNTJmMmRmODIzNDZjMDk0MzA4YTI1ODM2Nzg4NmUvdGFibGVyYW5nZTphZTA1MmYyZGY4MjM0NmMwOTQzMDhhMjU4MzY3ODg2ZV8wLTAtMS0xLTA_8fe7d1fa-f041-424a-be11-d0443f87368f">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGFibGU6YWUwNTJmMmRmODIzNDZjMDk0MzA4YTI1ODM2Nzg4NmUvdGFibGVyYW5nZTphZTA1MmYyZGY4MjM0NmMwOTQzMDhhMjU4MzY3ODg2ZV8wLTEtMS0xLTA_04ee164d-029c-446c-8d6c-f7e62da1616a">001-37985</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGFibGU6YWUwNTJmMmRmODIzNDZjMDk0MzA4YTI1ODM2Nzg4NmUvdGFibGVyYW5nZTphZTA1MmYyZGY4MjM0NmMwOTQzMDhhMjU4MzY3ODg2ZV8wLTItMS0xLTA_27342a6e-909b-445a-bdf6-9b97a8011a94">20-3828755</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzY5_812a72d5-9507-4058-9584-8e82474950ce">10770 Wateridge Circle</dei:EntityAddressAddressLine1>
    <dei:EntityAddressAddressLine2
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzU5_7c40accc-a7f7-43ae-a3b3-07aa87961110">Suite 210,</dei:EntityAddressAddressLine2>
    <dei:EntityAddressCityOrTown
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzYw_4ba8d4f1-e36c-4617-b043-8213619556b5">San Diego</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzcw_5fdcba01-aea7-4fd1-bc34-6a2f5da0b497">CA</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzYx_2e4b7340-a2a6-453b-a26a-4db0d5f31a50">92121</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzY1_10bcbf9e-17b2-461b-a543-d07d3258ba8c">858</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzcx_2cab9d63-58a0-4440-a576-a33951ad22a4">362-6295</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzcy_37795fd7-54e3-48f1-be26-17d3dc6ae6d1">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzYz_772b9b75-b7e8-4ced-aa61-dceb75f4debb">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzcz_3726193a-424f-46a6-b2fc-163e7dec332b">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzY2_526a917c-8be9-4709-8758-307e58c18455">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGFibGU6YWJhYjgyYjAzY2FmNGI3MjgzYzEwNzIxYTQyNDI4YTAvdGFibGVyYW5nZTphYmFiODJiMDNjYWY0YjcyODNjMTA3MjFhNDI0MjhhMF8xLTAtMS0xLTA_82b489ab-6cbd-415b-9ee6-06361bcd2311">Common Stock, par value $0.001 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGFibGU6YWJhYjgyYjAzY2FmNGI3MjgzYzEwNzIxYTQyNDI4YTAvdGFibGVyYW5nZTphYmFiODJiMDNjYWY0YjcyODNjMTA3MjFhNDI0MjhhMF8xLTEtMS0xLTA_59a3416e-b7b0-44ad-ad3a-fe3ccd0a46be">ANAB</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGFibGU6YWJhYjgyYjAzY2FmNGI3MjgzYzEwNzIxYTQyNDI4YTAvdGFibGVyYW5nZTphYmFiODJiMDNjYWY0YjcyODNjMTA3MjFhNDI0MjhhMF8xLTItMS0xLTA_5f470718-ed71-4496-af1a-e0de34331b75">NASDAQ</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="ia74c544141c34ba9aabe016a89e48b1a_D20210809-20210809"
      id="id3VybDovL2RvY3MudjEvZG9jOmU5MDIyOGE4ZDJjMDRlOTc5NWVjNzllNDdiMTYwZmI0L3NlYzplOTAyMjhhOGQyYzA0ZTk3OTVlYzc5ZTQ3YjE2MGZiNF8xL2ZyYWc6YWYxZWE2ZWY1MzA3NGU3MTlhMzJlN2Q5YThmMTgzNjQvdGV4dHJlZ2lvbjphZjFlYTZlZjUzMDc0ZTcxOWEzMmU3ZDlhOGYxODM2NF8xNzY3_78aadb47-db67-45bf-b2ec-e09863390f2d">false</dei:EntityEmergingGrowthCompany>
</xbrl>
