SEGMENTS - Major Product Categories and Percentage of Consolidated Net Sales (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Product Information [Line Items]
Net sales	$ 579,001	$ 580,908	$ 626,053	$ 533,174	$ 610,196	$ 553,073	$ 612,690	$ 491,319	$ 543,444	$ 425,098	$ 435,903	$ 362,716	$ 2,319,136	$ 2,267,278	$ 1,767,161
New trailers
Product Information [Line Items]
Net sales													1,662,679	1,638,373	1,413,689
Used trailers
Product Information [Line Items]
Net sales													2,479	13,132	13,998
Components, parts and service
Product Information [Line Items]
Net sales													140,489	145,250	154,526
Equipment and other
Product Information [Line Items]
Net sales													513,489	470,523	184,948
Commercial Trailer Products
Product Information [Line Items]
Net sales													1,519,592	1,536,687	1,348,251
Diversified Products
Product Information [Line Items]
Net sales													357,634	372,342	348,449
Final Mile Products
Product Information [Line Items]
Net sales													441,910	358,249	70,461
Operating Segments | Commercial Trailer Products
Product Information [Line Items]
Net sales													1,521,541	1,536,939	1,348,382
Operating Segments | Commercial Trailer Products | New trailers
Product Information [Line Items]
Net sales													1,464,636	1,473,583	1,273,584
Operating Segments | Commercial Trailer Products | Used trailers
Product Information [Line Items]
Net sales													435	9,618	10,720
Operating Segments | Commercial Trailer Products | Components, parts and service
Product Information [Line Items]
Net sales													40,344	34,994	48,008
Operating Segments | Commercial Trailer Products | Equipment and other
Product Information [Line Items]
Net sales													16,126	18,744	16,070
Operating Segments | Diversified Products
Product Information [Line Items]
Net sales													384,516	393,971	361,358
Operating Segments | Diversified Products | New trailers
Product Information [Line Items]
Net sales													198,043	164,790	140,105
Operating Segments | Diversified Products | Used trailers
Product Information [Line Items]
Net sales													2,044	3,514	3,278
Operating Segments | Diversified Products | Components, parts and service
Product Information [Line Items]
Net sales													113,024	122,099	117,681
Operating Segments | Diversified Products | Equipment and other
Product Information [Line Items]
Net sales													71,405	103,568	100,294
Operating Segments | Final Mile Products
Product Information [Line Items]
Net sales													441,910	358,249	70,461
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													15,023	9,968	1,877
Operating Segments | Final Mile Products | Equipment and other
Product Information [Line Items]
Net sales													426,887	348,281	68,584
Corporate and Eliminations
Product Information [Line Items]
Net sales													(28,831)	(21,881)	(13,040)
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													(27,902)	(21,811)	(13,040)
Corporate and Eliminations | Equipment and other
Product Information [Line Items]
Net sales													(929)	(70)	0
Corporate and Eliminations | Commercial Trailer Products
Product Information [Line Items]
Net sales													1,949	252	131
Corporate and Eliminations | Diversified Products
Product Information [Line Items]
Net sales													26,882	21,629	12,909
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													71.70%	72.20%	80.00%
Product Concentration Risk | Used trailers | Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													0.10%	0.60%	0.80%
Product Concentration Risk | Components, parts and service | Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													6.10%	6.40%	8.70%
Product Concentration Risk | Equipment and other | Sales revenue, net
Product Information [Line Items]
Percentage of consolidated net sales													22.10%	20.80%	10.50%