Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income		$ 2,312	$ 6,830	$ 3,896	$ 5,487
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment		(1,610)	1,818	(649)	(1,708)
Unrealized loss on cash flow hedges, net of tax benefit of $11, $0, $11, and $277, respectively		(33)	0	(33)	(809)
Cash flow hedges reclassified to earnings, net of tax expense of $99, $98, $295, and $98, respectively		136	137	409	137
Reclassification of pension liability adjustments to earnings, net of tax expense of $23, $15, $71, and $46, respectively*	[1]	92	66	274	200
Total comprehensive income		897	8,851	3,897	3,307
Less comprehensive loss attributable to noncontrolling interest:
Net loss attributable to noncontrolling interest		(30)	0	(64)	0
Foreign currency translation adjustment		(31)	0	(10)	0
Amounts attributable to noncontrolling interest		(61)	0	(74)	0
Comprehensive income attributable to L.B. Foster Company		$ 958	$ 8,851	$ 3,971	$ 3,307

[1] Reclassifications out of “Accumulated other comprehensive loss” for pension obligations are charged to “Selling and administrative expenses” within the Condensed Consolidated Statements of Operations.