<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2026"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="ash-20260730.xsd" xlink:type="simple"/>
    <context id="C_55274aa2-d063-489c-ba55-3d81c6ece967">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001674862</identifier>
        </entity>
        <period>
            <startDate>2026-07-30</startDate>
            <endDate>2026-07-30</endDate>
        </period>
    </context>
    <dei:AmendmentFlag
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_a499e97a-2033-4bef-be42-68a70dd8c0b3">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_49905708-1bbe-423b-9576-4cb45c93186f">0001674862</dei:EntityCentralIndexKey>
    <dei:DocumentType
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_dfb4817e-0932-49e9-a96c-92aa1eb9e71a">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_e0c5cafe-90d3-4eb1-8ee1-94c0ef16ba78">2026-07-30</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_27ace5a2-c55e-49ba-8a5a-1362aa688150">ASHLAND INC.</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_aa58d2f4-6dd8-4d2a-82dd-4ce5854a6a97">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_de52bf85-b083-457b-b21c-fa55d5f2c79b">333-211719</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_54524948-fd74-4644-8e46-770bbf49d10f">81-2587835</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_16b83e67-483d-46e7-bbab-ef16ad5a6950">8145 Blazer Drive</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_a2d0daeb-043e-4eb3-b3f3-50d6590a5794">Wilmington</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_12fe2620-3d77-49f7-b03d-0e25b2ee004c">DE</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_b5a84188-b80f-4b5a-9330-32c5f9bf6416">19808</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_4a66ea57-4280-4330-bd57-149d6fde1525">302</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_20a96c7e-9e2d-464e-a76c-89884a8834c1">995-3000</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_68d07e28-b438-4cbd-9904-e3db814958d1">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_3647d5c4-a442-4a5c-9c10-d59473cdab68">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_1ee889de-6a82-4414-935c-a1d41a7f698a">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_53754e0f-ba81-4bb8-8a62-0b4296c04948">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_38727a16-41f0-4a56-8270-2fa81195ef48">Common Stock, par value $.01 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_c2f78f1e-9af5-4697-aadb-280218ab48b8">ASH</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_7264e967-aadf-4bad-b941-a10f44f6c71f">NYSE</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="C_55274aa2-d063-489c-ba55-3d81c6ece967"
      id="F_8d7747de-e1a6-4bd6-963c-6ef763324693">false</dei:EntityEmergingGrowthCompany>
</xbrl>
