Summary of Significant Accounting Policies - Revision Adjustment to the Consolidated Statements of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	$ 543,744	$ 497,497
Total cost of sales	431,700	407,886
Gross profit	112,044	89,611
Selling and administrative expenses	97,623	82,657
Amortization expense (Note 5)	5,314	6,144
Operating income (loss)	9,107	(7,206)
Interest expense - net	5,528	3,340
Other expense (income) - net (Note 19)	2,635	(1,550)
Income (loss) before income taxes	944	(8,996)
Income tax (benefit) expense (Note 14)	(355)	36,681
Net income (loss)	1,299	(45,677)
Net loss attributable to noncontrolling interest	(165)	(113)
Net income (loss) attributable to L.B. Foster Company	$ 1,464	$ (45,564)
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)
Basic weighted average shares outstanding (in shares)	10,799,000	10,720,000
Diluted weighted average shares outstanding (in shares)	10,995,000	10,720,000
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	$ 543,744
Total cost of sales	430,934
Gross profit	112,810
Selling and administrative expenses	97,358
Amortization expense (Note 5)	5,314
Operating income (loss)	10,138
Interest expense - net	5,528
Other expense (income) - net (Note 19)	3,666
Income (loss) before income taxes	944
Income tax (benefit) expense (Note 14)	(355)
Net income (loss)	1,299
Net loss attributable to noncontrolling interest	(165)
Net income (loss) attributable to L.B. Foster Company	$ 1,464
Basic earnings (loss) per common share (usd per share)	$ 0.14
Diluted earnings (loss) per common share (usd per share)	$ 0.13
Basic weighted average shares outstanding (in shares)	10,799,000
Diluted weighted average shares outstanding (in shares)	10,995,000
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	$ 0
Total cost of sales	766
Gross profit	(766)
Selling and administrative expenses	265
Amortization expense (Note 5)	0
Operating income (loss)	(1,031)
Interest expense - net	0
Other expense (income) - net (Note 19)	(1,031)
Income (loss) before income taxes	0
Income tax (benefit) expense (Note 14)	0
Net income (loss)	0
Net loss attributable to noncontrolling interest	0
Net income (loss) attributable to L.B. Foster Company	$ 0
Basic earnings (loss) per common share (usd per share)	$ 0
Diluted earnings (loss) per common share (usd per share)	$ 0
Basic weighted average shares outstanding (in shares)	0
Diluted weighted average shares outstanding (in shares)	0
Sales of goods
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	$ 475,350	$ 436,821
Total cost of sales	368,197	355,106
Sales of goods | As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	475,350
Total cost of sales	367,431
Sales of goods | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	0
Total cost of sales	766
Sales of services
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	68,394	60,676
Total cost of sales	63,503	$ 52,780
Sales of services | As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	68,394
Total cost of sales	63,503
Sales of services | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total net sales (Note 4)	0
Total cost of sales	$ 0