Entity tax identification number Entity Tax Identification Number Rollover EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Maximum Maximum [Member] Legal Entity [Axis] Legal Entity [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] EBP, Description of Plan [Table] EBP, Description of Plan [Table] Mutual Funds Mutual Fund [Member] Selling Price EBP, Investment Sold, Excluding Plan Interest in Master Trust, Selling Price EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Pretax, maximum annual compensation to total compensation, percentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Self-Directed Brokerage Accounts EBP, Self-Directed Brokerage Account [Member] Total deductions EBP, Change in Net Asset Available for Benefit, Decrease Maximum borrowing, amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Fair Value Measurements EBP, Investment, Fair Value and NAV [Text Block] Minimum borrowing, amount EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Investments, at fair value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Money Markets Money Market Funds [Member] Level 1 Fair Value, Inputs, Level 1 [Member] NAV (in dollars per share) EBP, Net Asset Value per Share or Unit EBP, Investment, Fair Value and NAV [Abstract] Assets EBP, Asset [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Additions EBP, Change in Net Asset Available for Benefit, Increase [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Benefit Payments EBP, Payment to Participant [Policy Text Block] Unfunded commitments EBP, Fair Value, Investment, NAV, Unfunded Commitment Amendment Flag Amendment Flag Transfer of account balances, maximum percentage allowed to be invested in company stock EBP, Participant Contribution, Account Balance Transfer, Maximum Percentage Invested in Company Stock EBP, Participant Contribution, Account Balance Transfer, Maximum Percentage Invested in Company Stock Basis of Accounting EBP, Basis of Accounting [Policy Text Block] Deductions from net assets attributable to: EBP, Change in Net Asset Available for Benefit, Decrease From Net Assets [Abstract] EBP, Change in Net Asset Available for Benefit, Decrease From Net Assets EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] Investment, number of shares (in shares) EBP, Investment, Number of Shares EBP, Description of Plan and Accounting Change [Abstract] Receivables: EBP, Receivable [Abstract] EBP, Investment, Fair Value and NAV EBP, Investment, Fair Value and NAV [Table Text Block] Discretionary profit-sharing contribution, service period EBP, Discretionary Profit-Sharing Contribution, Service Period EBP, Discretionary Profit-Sharing Contribution, Service Period Common Stock Common Stock [Member] Investments [Domain] Investments [Domain] Use of Estimates EBP, Use of Estimate [Policy Text Block] Schedule H, Line 4i – Schedule of Assets (Held At End of Year) EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] Employee EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Investment, purchased, number of shares (in shares) EBP, Investment, Purchased, Number of Shares Minimum Minimum [Member] Investment Type [Axis] Investment Type [Axis] Interest income from notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Employer EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Interest and dividends EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Basis spread on variable rate EBP, Participant Loan, Basis Spread On Variable Rate EBP, Participant Loan, Basis Spread On Variable Rate Withdrawal age EBP, Withdrawal Age EBP, Withdrawal Age EBP, Description of Plan [Line Items] EBP, Description of Plan [Line Items] Plan number EBP, Plan Number Investment, Issuer Name [Axis] Investment, Issuer Name [Axis] EBP, Investment, Fair Value and NAV [Line Items] EBP, Investment, Fair Value and NAV [Line Items] Description of the Plan EBP, Description of Plan [Text Block] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] Common stocks EBP, Employer, Common Stock [Member] EBP, Schedule of Asset Held for Investment [Abstract] EBP, Accounting Policy [Table] EBP, Accounting Policy [Table] EBP, Asset Held for Investment, Participant Loan, Maturity Period EBP, Asset Held for Investment, Participant Loan, Maturity Period EBP, Asset Held for Investment, Participant Loan, Maturity Period Total Additions EBP, Change in Net Asset Available for Benefit, Increase Investment income: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Investment, Identifier [Axis] Investment, Identifier [Axis] Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Total EBP, Asset Held for Investment Risk and Uncertainties EBP, Risk and Uncertainty [Policy Text Block] Document Information [Line Items] Document Information [Line Items] Deemed distributions of notes receivable from participants EBP, Change in Net Asset Available for Benefit, Decrease from Deemed Distributions on Note Receivable from Participant EBP, Change in Net Asset Available for Benefit, Decrease from Deemed Distributions on Note Receivable from Participant Participant compensation matched, percentage EBP, Employer Contribution, Participant Compensation Matched, Percentage EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Investment sold, number of shares (in shares) EBP, Investment, Sold, Number of Shares Maximum amount invested in company stock, percentage EBP, Participant Contribution, Maximum Amount Invested in Company Stock, Percentage EBP, Participant Contribution, Maximum Amount Invested in Company Stock, Percentage EBP, Tax Status [Table] EBP, Tax Status [Table] Increase in net assets available for benefits EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Transactions with Parties-in-Interest EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Related Party and Party-in-Interest Transactions [Abstract] Retirement age EBP, Retirement Age EBP, Retirement Age EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Total receivables EBP, Receivable Net appreciation in value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Unrealized Gain (Loss) on Investment Benefit payments EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Fair Market Value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Early retirement, years of service EBP, Early Retirement, Years of Service EBP, Early Retirement, Years of Service Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] EBP, Statement of Net Asset Available for Benefit [Abstract] L.B. Foster Company L.B. Foster Company [Member] L.B. Foster Company Vesting period EBP, Employer Contribution Vesting Service Period Minimum Vesting service period for company contribution and/ or investment earning to the participant in Company Matching Contributions, Fixed Rate Contributions, Discretionary Profit-Sharing Contributions, Qualified Non-Elective Contributions, and Disability Contributions. EBP, Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] EBP, Tax Status [Abstract] Involuntary cash-out limit EBP, Involuntary Cash-out Limit EBP, Involuntary Cash-out Limit Early retirement age EBP, Early Retirement Age EBP, Early Retirement Age Primary residence, borrowing term EBP, Note Receivable From Participant, Account, Primary Residence, Maximum Borrowing Term EBP, Note Receivable From Participant, Account, Primary Residence, Maximum Borrowing Term EBP 201 EBP 201 [Member] EBP 201 Administrative Expenses EBP, Expense [Policy Text Block] Participant loan, current value EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Valuation of Investments and Income Recognition EBP, Investment [Policy Text Block] Total Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Document Type Document Type Entity Central Index Key Entity Central Index Key General loan, borrowing term EBP, Note Receivable From Participant, General Loan, Maximum Borrowing Term EBP, Note Receivable From Participant, General Loan, Maximum Borrowing Term Maximum after tax annual compensation to total compensation, percentage EBP, Participant Contribution, After Tax, Maximum Annual Contribution to Total Compensation, Percentage EBP, Participant Contribution, After Tax, Maximum Annual Contribution to Total Compensation, Percentage Participant loan, interest rate EBP, Asset Held for Investment, Participant Loan, Interest Rate Minimum hardship withdrawal limit EBP, Minimum Hardship Withdrawal Limit EBP, Minimum Hardship Withdrawal Limit EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] Deductions EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Notes receivable from participants EBP, Note Receivable from Participant Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Summary of Significant Accounting Policies EBP, Summary of Accounting Policy [Text Block] Entity Registrant Name Entity Registrant Name Third Party Issuer Third Party Issuer [Member] Third Party Issuer Aggregate cost EBP, Investment Acquired, Excluding Plan Interest in Master Trust, Cost Income Tax Status EBP, Tax Status [Text Block] Document Information [Table] Document Information [Table] Investment, Issuer Name [Domain] Investment, Issuer Name [Domain] Notes Receivable from Participants EBP, Note Receivable from Participant [Policy Text Block] Total investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Redemption, notice period EBP, Fair Value, Investment, NAV, Redemption, Notice Period EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Net assets available for benefits Net assets available for benefits, beginning of year Net assets available for benefits, end of year EBP, Net Asset Available for Benefit Entity [Domain] Entity [Domain] Contributions: EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Matching percentage EBP, Employer Contribution, Matching Percentage NAV Fair Value Measured at Net Asset Value Per Share [Member] EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items]