(Loss) Earnings Per Common Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Numerator for basic and diluted (loss) earnings per common share:
Net (loss) income attributable to L.B. Foster Company	$ (2,110)	$ 4,436
Denominator:
Weighted average shares outstanding (in shares)	10,540	10,762
Denominator for basic earnings per common share (in shares)	10,540	10,762
Effect of dilutive securities:
Stock compensation plans (in shares)	0	223
Dilutive potential common shares (in shares)	0	223
Denominator for diluted (loss) earnings per common share - adjusted weighted average shares outstanding (in shares)	10,540	10,985
Basic (loss) earnings per common share (in USD per share)	$ (0.20)	$ 0.41
Diluted (loss) earnings per common share (in USD per share)	$ (0.20)	$ 0.40
Anti-dilutive shares (in shares)	498