Revision of Prior Period Financial Statements - Consolidated Statements of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues	$ 58,307	$ 37,354	$ 32,370	$ 25,202	$ 69,724	$ 128,031	$ 47,857
Cost of sales	56,769	35,357	31,054	29,281	66,411	123,180	66,883
Gross profit	1,538	1,997	1,316	(4,079)	3,313	4,851	(19,026)
Selling, general and administrative expenses	5,701	6,294	9,151	7,158	15,445	21,146	21,105
Restructuring and impairment charges	(0)	(120)	6,650	30,103	6,530	6,530	31,250
Operating loss	(4,163)	(4,177)	(14,485)	(41,340)	(18,662)	(22,825)	(71,381)
Interest expense	(3,562)	(3,212)	(2,502)	(208)	(5,714)	(9,276)	(671)
Gain (loss) on change in fair market value of warrant liability	(293)	3,452	(22,128)	0	(18,676)	(18,969)	0
Other income	145	230	115	160	345	490	518
Income (loss) before income taxes	2,256	(3,707)	(39,000)	(41,388)	(42,707)	(40,451)	(71,534)
Income tax provision	1,525	504	132	(75)	636	2,161	(78)
Net income (loss)	731	(4,211)	(39,132)	(41,313)	(43,343)	(42,612)	(71,456)
Less Net loss attributable to noncontrolling interest in JV	0	0	0	(991)	0	0	(1,396)
Net income (loss) attributable to FreightCar America	$ 731	$ (4,211)	$ (39,132)	$ (40,322)	$ (43,343)	$ (42,612)	$ (70,060)
Net income (loss) per common share attributable to FreightCar America- basic	$ 0.03	$ (0.24)	$ (1.96)	$ (3.03)	$ (2.19)	$ (2.11)	$ (5.30)
Net income (loss) per common share attributable to FreightCar America- diluted	$ 0.03	$ (0.24)	$ (1.96)	$ (3.03)	$ (2.19)	$ (2.11)	$ (5.30)
Weighted average common shares outstanding - basic	20,485,438	20,160,410	20,001,505	12,426,872	20,084,199	20,225,671	12,399,687
Weighted average common shares outstanding - diluted	22,111,824	20,160,410	20,001,505	12,426,872	20,084,199	20,225,671	12,399,687
As Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		$ 37,354	$ 32,370		$ 69,724
Cost of sales		33,716	29,780		63,496
Gross profit		3,638	2,590		6,228
Selling, general and administrative expenses		6,294	9,151		15,445
Restructuring and impairment charges		(120)	6,650		6,530
Operating loss		(2,536)	(13,211)		(15,747)
Interest expense		(3,212)	(2,502)		(5,714)
Gain (loss) on change in fair market value of warrant liability		3,452	(22,128)		(18,676)
Other income		230	115		345
Income (loss) before income taxes		(2,066)	(37,726)		(39,792)
Income tax provision		504	132		636
Net income (loss)		(2,570)	(37,858)		(40,428)
Less Net loss attributable to noncontrolling interest in JV		0	0		0
Net income (loss) attributable to FreightCar America		$ (2,570)	$ (37,858)		$ (40,428)
Net income (loss) per common share attributable to FreightCar America- basic		$ (0.13)	$ (1.89)		$ (2.01)
Net income (loss) per common share attributable to FreightCar America- diluted		$ (0.13)	$ (1.89)		$ (2.01)
Weighted average common shares outstanding - basic		20,160,410	20,001,505		20,084,199
Weighted average common shares outstanding - diluted		20,160,410	20,001,505		20,084,199
Adjustments [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of sales		$ 1,641	$ 1,274		$ 2,915
Gross profit		(1,641)	(1,274)		(2,915)
Operating loss		(1,641)	(1,274)		(2,915)
Income (loss) before income taxes		(1,641)	(1,274)		(2,915)
Income tax provision		0	0		0
Net income (loss)		(1,641)	(1,274)		(2,915)
Less Net loss attributable to noncontrolling interest in JV		0	0		0
Net income (loss) attributable to FreightCar America		$ (1,641)	$ (1,274)		$ (2,915)
Net income (loss) per common share attributable to FreightCar America- basic		$ (0.11)	$ (0.07)		$ (0.18)
Net income (loss) per common share attributable to FreightCar America- diluted		$ (0.11)	$ (0.07)		$ (0.18)