SEGMENTS - Major Product Categories and Percentage of Consolidated Net Sales (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Product Information [Line Items]
Net sales	$ 404,078	$ 351,584	$ 339,153	$ 387,074	$ 579,001	$ 580,908	$ 626,053	$ 533,174	$ 610,196	$ 553,073	$ 612,690	$ 491,319	$ 1,481,889	$ 2,319,136	$ 2,267,278
New trailers
Product Information [Line Items]
Net sales													1,087,820	1,662,679	1,638,373
Used trailers
Product Information [Line Items]
Net sales													8,386	2,479	13,132
Components, parts and service
Product Information [Line Items]
Net sales													114,048	140,489	145,250
Equipment and other
Product Information [Line Items]
Net sales													271,635	513,489	470,523
Commercial Trailer Products
Product Information [Line Items]
Net sales													992,528	1,519,592	1,536,687
Diversified Products
Product Information [Line Items]
Net sales													270,963	357,634	372,342
Final Mile Products
Product Information [Line Items]
Net sales													218,398	441,910	358,249
Operating Segments \| Commercial Trailer Products
Product Information [Line Items]
Net sales													992,776	1,521,541	1,536,939
Operating Segments \| Commercial Trailer Products \| New trailers
Product Information [Line Items]
Net sales													941,932	1,464,636	1,473,583
Operating Segments \| Commercial Trailer Products \| Used trailers
Product Information [Line Items]
Net sales													3,841	435	9,618
Operating Segments \| Commercial Trailer Products \| Components, parts and service
Product Information [Line Items]
Net sales													36,912	40,344	34,994
Operating Segments \| Commercial Trailer Products \| Equipment and other
Product Information [Line Items]
Net sales													10,091	16,126	18,744
Operating Segments \| Diversified Products
Product Information [Line Items]
Net sales													294,134	384,516	393,971
Operating Segments \| Diversified Products \| New trailers
Product Information [Line Items]
Net sales													145,888	198,043	164,790
Operating Segments \| Diversified Products \| Used trailers
Product Information [Line Items]
Net sales													4,545	2,044	3,514
Operating Segments \| Diversified Products \| Components, parts and service
Product Information [Line Items]
Net sales													88,010	113,024	122,099
Operating Segments \| Diversified Products \| Equipment and other
Product Information [Line Items]
Net sales													55,691	71,405	103,568
Operating Segments \| Final Mile Products
Product Information [Line Items]
Net sales													218,398	441,910	358,249
Operating Segments \| Final Mile Products \| New trailers
Product Information [Line Items]
Net sales													0		0
Operating Segments \| Final Mile Products \| Used trailers
Product Information [Line Items]
Net sales													0	0	0
Operating Segments \| Final Mile Products \| Components, parts and service
Product Information [Line Items]
Net sales													12,517	15,023	9,968
Operating Segments \| Final Mile Products \| Equipment and other
Product Information [Line Items]
Net sales													205,881	426,887	348,281
Corporate and Eliminations
Product Information [Line Items]
Net sales													(23,419)	(28,831)	(21,881)
Corporate and Eliminations \| New trailers
Product Information [Line Items]
Net sales													0	0	0
Corporate and Eliminations \| Used trailers
Product Information [Line Items]
Net sales													0	0	0
Corporate and Eliminations \| Components, parts and service
Product Information [Line Items]
Net sales													(23,391)	(27,902)	(21,811)
Corporate and Eliminations \| Equipment and other
Product Information [Line Items]
Net sales													(28)	(929)	(70)
Corporate and Eliminations \| Commercial Trailer Products
Product Information [Line Items]
Net sales													248	1,949	252
Corporate and Eliminations \| Diversified Products
Product Information [Line Items]
Net sales													23,171	26,882	21,629
Corporate and Eliminations \| Final Mile Products
Product Information [Line Items]
Net sales													$ 0	$ 0	$ 0
Product Concentration Risk \| Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													100.00%	100.00%	100.00%
Product Concentration Risk \| New trailers \| Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													73.40%	71.70%	72.20%
Product Concentration Risk \| Used trailers \| Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													0.60%	0.10%	0.60%
Product Concentration Risk \| Components, parts and service \| Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													7.70%	6.10%	6.40%
Product Concentration Risk \| Equipment and other \| Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													18.30%	22.10%	20.80%