Earning Per Common Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Numerator for basic and diluted earnings per common share:
Net income attributable to L.B. Foster Company	$ 2,847	$ 3,531	$ 7,283	$ 1,379
Denominator:
Weighted average shares outstanding (in shares)	10,793	10,807	10,777	10,800
Denominator for basic earnings per common share (in shares)	10,793	10,807	10,777	10,800
Effect of dilutive securities:
Stock compensation plans (in shares)	267	71	285	66
Dilutive potential common shares (in shares)	267	71	285	66
Denominator for diluted earnings per common share - adjusted weighted average shares outstanding (in shares)	11,060	10,878	11,062	10,866
Basic earnings per common share (in USD per share)	$ 0.26	$ 0.32	$ 0.68	$ 0.12
Diluted earnings per common share (in USD per share)	$ 0.26	$ 0.32	$ 0.66	$ 0.12