<?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-20211104.xsd" xlink:type="simple"/>
    <context id="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001370053</identifier>
        </entity>
        <period>
            <startDate>2021-11-04</startDate>
            <endDate>2021-11-04</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF80L2ZyYWc6OTM1ZTRjZDEwMmQ5NDU3NWJmNTI0ZjEwNDQ2ODliNzUvdGFibGU6Yzk4YTM5YzVmNmFjNDIyY2I3NmM0MDc3YzA5MzNiY2EvdGFibGVyYW5nZTpjOThhMzljNWY2YWM0MjJjYjc2YzQwNzdjMDkzM2JjYV8yLTEtMS0xLTgyODU_466f4329-0565-4706-b986-309995154c9d">0001370053</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF80L2ZyYWc6OTM1ZTRjZDEwMmQ5NDU3NWJmNTI0ZjEwNDQ2ODliNzUvdGFibGU6Yzk4YTM5YzVmNmFjNDIyY2I3NmM0MDc3YzA5MzNiY2EvdGFibGVyYW5nZTpjOThhMzljNWY2YWM0MjJjYjc2YzQwNzdjMDkzM2JjYV81LTEtMS0xLTgyODU_08043971-20a0-4e8d-b0c6-8f0a3829d6a3">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzU4_6c3adb83-83a3-42df-ace3-8485d6c0aaaf">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xOTE_df57f66a-8e43-4b33-a28f-02b25762b9b3">2021-11-04</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzU5_7d04ac27-028d-4323-8672-442fab9af62d">ANAPTYSBIO, INC</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGFibGU6NDRkMzBjOGJkNWNiNDc1MmEwNGQ3NDA4NDZlNjBiMDYvdGFibGVyYW5nZTo0NGQzMGM4YmQ1Y2I0NzUyYTA0ZDc0MDg0NmU2MGIwNl8wLTAtMS0xLTgyODU_09424789-ed70-4b50-b126-6b1c4f300471">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGFibGU6NDRkMzBjOGJkNWNiNDc1MmEwNGQ3NDA4NDZlNjBiMDYvdGFibGVyYW5nZTo0NGQzMGM4YmQ1Y2I0NzUyYTA0ZDc0MDg0NmU2MGIwNl8wLTEtMS0xLTgyODU_6ff47d4d-6f8b-481a-8561-cc40734923ee">001-37985</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGFibGU6NDRkMzBjOGJkNWNiNDc1MmEwNGQ3NDA4NDZlNjBiMDYvdGFibGVyYW5nZTo0NGQzMGM4YmQ1Y2I0NzUyYTA0ZDc0MDg0NmU2MGIwNl8wLTItMS0xLTgyODU_123126a7-d31f-4f53-9ead-62ccf9a77997">20-3828755</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzY0_bdf21beb-1d4b-4691-b0af-65e0ebc05019">10770 Wateridge Circle</dei:EntityAddressAddressLine1>
    <dei:EntityAddressAddressLine2
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzY1_5e98e40b-06e1-4ef2-900d-d0e7068e1dbe">Suite 210,</dei:EntityAddressAddressLine2>
    <dei:EntityAddressCityOrTown
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzcw_37ab1539-3181-47f4-ab96-d163ed8a4dfe">San Diego</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzcx_ef014fd9-eeb1-45ca-a3f4-27e68ea07a9d">CA</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzY2_f8390795-3367-47ca-8c12-3f4c61296750">92121</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzY3_58d9c8e8-535f-4e07-b4a2-9cf581f7019a">858</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzcy_5c06c339-339e-45c4-b4eb-30adb2c43052">362-6295</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzYx_9771bb4d-b2c7-4e16-a2bf-c5f0605ee6bb">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzY4_ff2dcfd1-8e08-427f-9a01-13e1791a5553">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzYy_87bbc67e-da0e-4352-b961-58df168cf9d5">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzU3_53706bd2-0b20-4402-8c4e-09b9e20603a5">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGFibGU6MTUxYTFjYWFlZjcwNDExMzliYzA5YjFlYTBkNzVjMTcvdGFibGVyYW5nZToxNTFhMWNhYWVmNzA0MTEzOWJjMDliMWVhMGQ3NWMxN18xLTAtMS0xLTgyODU_cd2ba1ff-3e41-4e79-a35f-5a0df5981ab4">Common Stock, par value $0.001 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGFibGU6MTUxYTFjYWFlZjcwNDExMzliYzA5YjFlYTBkNzVjMTcvdGFibGVyYW5nZToxNTFhMWNhYWVmNzA0MTEzOWJjMDliMWVhMGQ3NWMxN18xLTEtMS0xLTgyODU_c702551f-b55c-451c-8110-aee0ab7ea0ee">ANAB</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGFibGU6MTUxYTFjYWFlZjcwNDExMzliYzA5YjFlYTBkNzVjMTcvdGFibGVyYW5nZToxNTFhMWNhYWVmNzA0MTEzOWJjMDliMWVhMGQ3NWMxN18xLTItMS0xLTgyODU_778a4a23-6329-4c8b-925c-6a9ba946cde1">NASDAQ</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="i3052f4f6865b4f5aa705f4587827d448_D20211104-20211104"
      id="id3VybDovL2RvY3MudjEvZG9jOjA5MjM1NmY4YmU0YjRmNGFiMTdlNThjMzY1ZjYyZTk4L3NlYzowOTIzNTZmOGJlNGI0ZjRhYjE3ZTU4YzM2NWY2MmU5OF8xL2ZyYWc6OGE3YzY5MTYxMDE1NDgzOGI4ZDgyNzZjZmEyMWU4YmYvdGV4dHJlZ2lvbjo4YTdjNjkxNjEwMTU0ODM4YjhkODI3NmNmYTIxZThiZl8xNzcz_44df511b-56d2-4de1-a7dd-fdc637ae3374">false</dei:EntityEmergingGrowthCompany>
</xbrl>
