Earnings Per Common Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Numerator for basic and diluted earnings (loss) per common share:
Net income (loss) attributable to L.B. Foster Company	$ 1,464	$ (45,564)
Denominator:
Weighted average shares outstanding (in shares)	10,799,000	10,720,000
Denominator for basic earnings per common share (in shares)	10,799,000	10,720,000
Effect of dilutive securities:
Stock compensation plans (in shares)	196,000	0
Dilutive potential common shares (in shares)	196,000	0
Denominator for diluted earnings per common share - adjusted weighted average shares outstanding and assumed conversions (in shares)	10,995,000	10,720,000
Basic earnings (loss) per common share (usd per share)	$ 0.14	$ (4.25)
Diluted earnings (loss) per common share (usd per share)	$ 0.13	$ (4.25)
Anti-dilutive share (in shares)	0	75,000