<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2025"
  xmlns:itw="http://www.itw.com/20260811"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:us-gaap="http://fasb.org/us-gaap/2025"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="itw-20260811.xsd" xlink:type="simple"/>
    <context id="duration_2026-08-11_to_2026-08-11">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:CommonStockMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A0.625EuroNotesdue2027Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">itw:A0.625EuroNotesdue2027Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.250EuroNotesDue2028Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">itw:A3.250EuroNotesDue2028Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A2.125EuroNotesdue2030Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">itw:A2.125EuroNotesdue2030Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A1.00EuroNotesdue2031Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">itw:A1.00EuroNotesdue2031Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.375EuroNotesDue2032Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">itw:A3.375EuroNotesDue2032Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <context id="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.00EuroNotesdue2034Member">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000049826</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">itw:A3.00EuroNotesdue2034Member</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-08-11</startDate>
            <endDate>2026-08-11</endDate>
        </period>
    </context>
    <dei:EntityRegistrantName
      contextRef="duration_2026-08-11_to_2026-08-11"
      id="Hidden_dei_EntityRegistrantName">ILLINOIS TOOL WORKS INC</dei:EntityRegistrantName>
    <dei:AmendmentFlag contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-357">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="duration_2026-08-11_to_2026-08-11"
      id="Hidden_dei_EntityCentralIndexKey">0000049826</dei:EntityCentralIndexKey>
    <dei:DocumentType contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-424">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-425">2026-08-11</dei:DocumentPeriodEndDate>
    <dei:EntityIncorporationStateCountryCode contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-426">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-427">1-4797</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-428">36-1258310</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1 contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-429">155 Harlem Avenue</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-430">Glenview</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-431">IL</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-432">60025</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-433">847</dei:CityAreaCode>
    <dei:LocalPhoneNumber contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-434">724-7500</dei:LocalPhoneNumber>
    <dei:Security12bTitle
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember"
      id="ixv-435">Common Stock</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember"
      id="ixv-436">ITW</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_us-gaap-CommonStockMember"
      id="ixv-437">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A0.625EuroNotesdue2027Member"
      id="ixv-438">0.625% Euro Notes due 2027</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A0.625EuroNotesdue2027Member"
      id="ixv-439">ITW27</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A0.625EuroNotesdue2027Member"
      id="ixv-440">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.250EuroNotesDue2028Member"
      id="ixv-441">3.250% Euro Notes due 2028</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.250EuroNotesDue2028Member"
      id="ixv-442">ITW28</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.250EuroNotesDue2028Member"
      id="ixv-443">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A2.125EuroNotesdue2030Member"
      id="ixv-444">2.125% Euro Notes due 2030</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A2.125EuroNotesdue2030Member"
      id="ixv-445">ITW30</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A2.125EuroNotesdue2030Member"
      id="ixv-446">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A1.00EuroNotesdue2031Member"
      id="ixv-447">1.00% Euro Notes due 2031</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A1.00EuroNotesdue2031Member"
      id="ixv-448">ITW31</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A1.00EuroNotesdue2031Member"
      id="ixv-449">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.375EuroNotesDue2032Member"
      id="ixv-450">3.375% Euro Notes due 2032</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.375EuroNotesDue2032Member"
      id="ixv-451">ITW32</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.375EuroNotesDue2032Member"
      id="ixv-452">NYSE</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.00EuroNotesdue2034Member"
      id="ixv-453">3.00% Euro Notes due 2034</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.00EuroNotesdue2034Member"
      id="ixv-454">ITW34</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="duration_2026-08-11_to_2026-08-11_us-gaap-StatementClassOfStockAxis_itw-A3.00EuroNotesdue2034Member"
      id="ixv-455">NYSE</dei:SecurityExchangeName>
    <dei:WrittenCommunications contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-456">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-457">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-458">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-459">false</dei:PreCommencementIssuerTenderOffer>
    <dei:EntityEmergingGrowthCompany contextRef="duration_2026-08-11_to_2026-08-11" id="ixv-460">false</dei:EntityEmergingGrowthCompany>
</xbrl>
