Document and Entity Information [Abstract] Document Information [Table] Legal Entity [Axis] Entity [Domain] Represents the Retirement Plan No 003. E B P 003 [Member] EMPLOYEE RETIREMENT SAVINGS PLAN Document Information [Line Items] Document and Entity Information Document Type Entity Registrant Name Entity Central Index Key Amendment Flag STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS EBP, Statement of Net Asset Available for Benefit [Table] Investment Type [Axis] Investments [Domain] Common Collective Trust [Member] Common collective trust funds Common collective trust Represents information pertaining to stable value fund which is common collective trust fund. Employee Benefit Plan, Common Collective Trust, Stable Value Fund [Member] Stable value fund Represents information pertaining to other common collective trust fund other than stable value fund. Employee Benefit Plan, Common Collective Trust, Other Than Stable Value Fund [Member] Common collective trusts Mutual Fund [Member] Mutual funds Mutual fund EBP, Employer, Common Stock [Member] Valmont Industries, Inc. common stock Common stock EBP, Statement of Net Asset Available for Benefit [Line Items] STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS EBP, Asset [Abstract] Assets EBP, Investment, Fair Value [Abstract] Investments, at fair value: EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Total investments, at fair value EBP, Receivable [Abstract] Receivables: EBP, Note Receivable from Participant Notes receivable from participants EBP, Investment Income, Receivable Due from broker for securities sold EBP, Receivable Total receivables EBP, Liability [Abstract] Liabilities: EBP, Excess Contribution Payable Excess contributions payable EBP, Net Asset Available for Benefit End of year Beginning of year Net assets available for benefits STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS EBP, Change in Net Asset Available for Benefit, Increase [Abstract] Additions to net assets attributed to: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Investment income: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Net appreciation in investments EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Interest and dividends on investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Net investment income EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Interest income on notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Contributions: EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash Employer EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Participant EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Rollover EBP, Change in Net Asset Available for Benefit, Increase from Contribution Total contributions EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Deductions from net assets attributed to: EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Benefits paid to participants EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Administrative expenses Fees paid by Plan participants EBP, Change in Net Asset Available for Benefit, Decrease Total deductions EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Change in net assets available for benefits EBP, Change in Net Asset Available for Benefit, Increase (Decrease) [Abstract] Net assets available for benefits: DESCRIPTION OF THE PLAN EBP, Description of Plan [Table] EBP, Description of Plan [Line Items] DESCRIPTION OF THE PLAN PLAN TERMINATION EBP, Description of Plan [Text Block] DESCRIPTION OF THE PLAN SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EBP, Accounting Policy [Table] EBP, Accounting Policy [Line Items] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EBP, Summary of Accounting Policy [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES FAIR VALUE MEASUREMENTS EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Line Items] FAIR VALUE MEASUREMENTS EBP, Investment, Fair Value and NAV [Text Block] FAIR VALUE MEASUREMENTS PARTY-IN-INTEREST TRANSACTIONS EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Line Items] PARTY-IN-INTEREST TRANSACTIONS EBP, Related Party and Party-in-Interest Transactions [Text Block] PARTY-IN-INTEREST TRANSACTIONS No definition available. PLAN TERMINATION EBP, Plan Termination [Text Block] PLAN TERMINATION FEDERAL INCOME TAX STATUS EBP, Tax Status [Table] EBP, Tax Status [Line Items] FEDERAL INCOME TAX STATUS EBP, Tax Status [Text Block] FEDERAL INCOME TAX STATUS FORM 5500, SCHEDULE H, PART IV, LINE 4(i) - SCHEDULE OF ASSETS (HELD AT END OF YEAR) EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Line Items] FORM 5500, SCHEDULE H, PART IV, LINE 4(i) - SCHEDULE OF ASSETS (HELD AT END OF YEAR) EBP, Schedule of Asset Held for Investment [Text Block] FORM 5500, SCHEDULE H, PART IV, LINE 4(i) - SCHEDULE OF ASSETS (HELD AT END OF YEAR) EBP, Basis of Accounting [Policy Text Block] Basis of Accounting EBP, Use of Estimate [Policy Text Block] Use of Estimates EBP, Risk and Uncertainty [Policy Text Block] Risks and Uncertainties EBP, Investment [Policy Text Block] Investment Valuation and Income Recognition EBP, Note Receivable from Participant [Policy Text Block] Notes Receivable from Participants EBP, Expense [Policy Text Block] Administrative Expenses EBP, Payment to Participant [Policy Text Block] Payment of Benefits EBP, Excess Contribution Payable [Policy Text Block] Excess Contributions Payable EBP, Investment, Fair Value and NAV [Table Text Block] Schedule of Plan's Assets Fair Value Hierarchy EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Employee contribution EBP, Participant Contribution, Automatic, Deferral Rate Deferral rate EBP, Employer Contribution, Matching Percentage Employer contribution EBP, Employer Contribution, Participant Compensation Matched, Percentage Percentage of participant eligible compensation Percentage of increase in investments under various categories of investment. Employee Benefit Plan, Percentage Of Increase In Investment Percentage of increments in various investment options Percentage of maximum investment in employer's company common stock. Employee Benefit Plan, Maximum Percentage Of Investment In Employer Stock Maximum percentage of investment in Valmont Stock Fund Represents the percentage of vesting. Employee Benefit Plan, Vesting Percentage Vesting percentage Represents the period of vesting. Employee Benefit Plan, Vesting Period Vesting period EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Note receivable, minimum borrowing amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Note receivable, maximum borrowing amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage Note receivable, maximum borrowing percentage Represents the maximum number of notes receivable from participants outstanding . Employee Benefit Plan, Note Receivable From Participant, Maximum Number Of Loans Outstanding Note receivable, maximum number of loans outstanding Maximum term of participant loan of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Note Receivable From Participant, Maximum Term Maximum loan term EBP, Forfeited Nonvested Account Forfeited nonvested account balance EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Amount of forfeited nonvested accounts used to offset employer contributions Scenario [Axis] Scenario [Domain] Represents the information pertaining to scenario in which withdrawal is initiated by plan sponsor. Initiated By Plan Sponsor [Member] Initiated by Plan Sponsor EBP, Fair Value, Investment, NAV, Redemption, Notice Period Redemption notice EBP, Liability to Participant Benefits payable Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Measured at Net Asset Value Per Share [Member] Net asset value Represents information pertaining to normal scenario of the fund. Employee Benefit Plan, General [Member] General Represents information pertaining to scenario in which plan initiates full redemption of the fund. Employee Benefit Plan, Full Redemption Of Fund [Member] Full redemption of the fund Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Fair value hierarchy Fair Value, Inputs, Level 1 [Member] Level 1 EBP, Related Party and Party-in-Interest [Axis] EBP, Related Party and Party-in-Interest [Domain] EBP, Trustee [Member] Fidelity Represents information pertaining to employer. Employee Benefit Plan, Employer [Member] Employer EBP, Investment, Number of Shares Number of Shares Number of shares held EBP, Investment, Excluding Plan Interest in Master Trust, Cost Investment at cost basis EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Dividend income Percentage of plan participants contribution vesting percentage in the event of plan termination. Employee Benefit Plan, Plan Termination, Participant Contribution, Vesting Percentage Vesting percentage EBP, Tax Determination Letter, Obtained [true false] Determination letter obtained EBP, Tax Determination Letter, Date Determination letter date EBP, Tax Qualification Status [Extensible Enumeration] Tax qualification status Investment, Identifier [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Minimum [Member] Minimum Maximum [Member] Maximum Entity Tax Identification Number Entity tax identification number EBP, Plan Number Plan number EBP, Investment, Issuer Name [Extensible Enumeration] Issuer name EBP, Investment, Current Value, Type [Extensible Enumeration] Investment curent value type EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Current Value EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Notes receivable from participants EBP, Asset Held for Investment, Participant Loan, Interest Rate Interest rates of notes receivable from participants EBP, Asset Held for Investment Total Investments and Loans EBP, Asset Held for Investment, Party-in-Interest [true false] Party-in-Interest EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] Participation Status