Earning Per Common Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Numerator for basic and diluted earnings per common share:
Income from continuing operations attributable to L.B. Foster Company	$ 3,554	$ 25,823
Income (loss) from discontinued operations	72	(18,241)
Net income attributable to L.B. Foster Company	$ 3,626	$ 7,582
Denominator:
Weighted average shares outstanding (shares)	10,623,000	10,540,000
Denominator for basic earnings per common share (shares)	10,623,000	10,540,000
Effect of dilutive securities:
Stock compensation plans (shares)	129,000	131,000
Dilutive potential common shares (shares)	129,000	131,000
Denominator for diluted earnings per common share - adjusted weighted average shares outstanding and assumed conversions (shares)	10,752,000	10,671,000
Basic earnings from continuing operations (usd per share)	$ 0.33	$ 2.45
Basic earnings (loss) from discontinued operations per common share (usd per share)	0.01	(1.73)
Basic earnings per common share (usd per share)	0.34	0.72
Diluted earnings from continuing operations per common share (usd per share)	0.33	2.42
Diluted earnings (loss) from discontinued operations per common share (usd per share)	0.01	(1.71)
Diluted earnings per common share (usd per share)	$ 0.34	$ 0.71
Anti-dilutive share (shares)	0	0