SEGMENTS - Reportable Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Net sales
Total net sales	$ 351,584	$ 580,908	$ 1,077,811	$ 1,740,135
Income (loss) from operations	8,408	38,269	(95,649)	111,005
Assets	1,196,082	1,378,603	1,196,082	1,378,603	$ 1,304,591
Commercial Trailer Products Segment
Net sales
Total net sales	226,324	380,062	709,516	1,120,608
Diversified Products Segment
Net sales
Total net sales	69,912	87,342	201,845	270,357
Final Mile Products Segment
Net sales
Total net sales	55,348	113,504	166,450	349,170
Corporate and Eliminations
Net sales
Total net sales	(2,300)	(6,121)	(17,313)	(21,143)
Income (loss) from operations	(10,997)	(10,045)	(31,086)	(31,593)
Assets	193,897	179,422	193,897	179,422
Corporate and Eliminations | Commercial Trailer Products Segment
Net sales
Total net sales	192	282	229	1,645
Corporate and Eliminations | Diversified Products Segment
Net sales
Total net sales	2,108	5,839	17,084	19,498
Corporate and Eliminations | Final Mile Products Segment
Net sales
Total net sales	0	0	0	0
Operating Segments | Commercial Trailer Products Segment
Net sales
Total net sales	226,516	380,344	709,745	1,122,253
Income (loss) from operations	19,659	36,503	54,129	102,742
Assets	326,908	364,436	326,908	364,436
Operating Segments | Diversified Products Segment
Net sales
Total net sales	72,020	93,181	218,929	289,855
Income (loss) from operations	4,188	7,183	360	24,138
Assets	287,788	327,343	287,788	327,343
Operating Segments | Final Mile Products Segment
Net sales
Total net sales	55,348	113,504	166,450	349,170
Income (loss) from operations	(4,442)	4,628	(119,052)	15,718
Assets	$ 387,489	$ 507,402	$ 387,489	$ 507,402