<?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="vmi-20260721.xsd" xlink:type="simple"/>
    <context id="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000102729</identifier>
        </entity>
        <period>
            <startDate>2026-07-21</startDate>
            <endDate>2026-07-21</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_Dv-x6Vf3pkK32PFaOO_a0A_1_1">0000102729</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_Ppu5l-TKhUyzHQECLDTiOw_2_1">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_rREGMIfyDkSm3htdAMxTqA">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_P8BJSX0T606A9B_sOez0KQ">2026-07-21</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_1KUOK0OdUEqSVOErv4q__Q">Valmont Industries, Inc.</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_ewyitzxpwUigI31ysq1VCQ">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_smnnDji3I0eb2ahhJxfiRQ_0_0">1-31429</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_7LBsb-UE-kuU5T04CzrOJQ_0_2">47-0351813</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_aMW9npWmN0WRKIy3I3HXFg_3_0">15000 Valmont Plaza</dei:EntityAddressAddressLine1>
    <dei:EntityAddressPostalZipCode
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_xLm3pt3coEyDOHyoWaZU0Q_3_2">68154</dei:EntityAddressPostalZipCode>
    <dei:EntityAddressCityOrTown
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_6L5TwpQ3QkKCUWZVtmr7aA">Omaha,</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_moNnhzDcz0C-32SCzPvl-w">NE</dei:EntityAddressStateOrProvince>
    <dei:CityAreaCode
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_laPGp-37IUCLQ5HuitBxGA">402</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_7wG7vAUsBUClFXUB5JBJCA">963-1000</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_cFSUBZyb2EOd6gsEEkE99A">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_pkBKUgF2LUi6_okEpPGCww">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_JV2xMxjZo0e1K2WqurpbOQ">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_BIF1fql7Y0S0d2zxdTxKXA">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_nCZAfQgV5UKgWPVDCaSOQA_2_0">Common Stock, $1.00 par value</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_NWxf1mge7kia4oF8EKjueg_2_2">VMI</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Tc_iEy6_H7rs06HBZe_4uWRhg_2_4">NYSE</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="Duration_7_21_2026_To_7_21_2026_HBjpjjC3_0-IsUl1a08bHQ"
      id="Narr_2xCWwXLtT0y4B5PN0kQY_A">false</dei:EntityEmergingGrowthCompany>
</xbrl>
