Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (Loss)		$ 2,854	$ 523	$ 1,584	$ (1,343)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment		538	181	961	(3,526)
Unrealized gain (loss) on cash flow hedges, net of tax expense (benefit) of $0, $19, $0, and $(277), respectively		0	55	0	(809)
Cash flow hedges reclassified to earnings, net of tax expense of $98, $0, $196, and $0, respectively		137	0	273	0
Reclassification of pension liability adjustments to earnings, net of tax expense of $24, $31, $48, and $55, respectively*	[1]	91	76	182	134
Total comprehensive income (loss)		3,620	835	3,000	(5,544)
Less comprehensive income (loss) attributable to noncontrolling interest:
Net loss attributable to noncontrolling interest		(22)	0	(34)	0
Foreign currency translation adjustment		51	0	21	0
Amounts attributable to noncontrolling interest		29	0	(13)	0
Comprehensive income (loss) attributable to L.B. Foster Company		$ 3,591	$ 835	$ 3,013	$ (5,544)

[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.