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		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Numerator for basic and diluted earnings per common share:
Net income attributable to L.B. Foster Company	$ 2,885	$ 2,847	$ 775	$ 7,283
Denominator:
Weighted average shares outstanding (in shares)	10,439	10,793	10,489	10,777
Denominator for basic earnings per common share (in shares)	10,439	10,793	10,489	10,777
Effect of dilutive securities:
Stock compensation plans (in shares)	414	267	456	285
Dilutive potential common shares (in shares)	414	267	456	285
Denominator for diluted earnings per common share - adjusted weighted average shares outstanding (in shares)	10,853	11,060	10,945	11,062
Basic earnings per common share (in USD per share)	$ 0.28	$ 0.26	$ 0.07	$ 0.68
Diluted earnings per common share (in USD per share)	$ 0.27	$ 0.26	$ 0.07	$ 0.66