SEGMENTS - Major Product Categories and Percentage of Consolidated Net Sales (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Product Information [Line Items]
Net sales	$ 482,566	$ 351,584	$ 1,323,991	$ 1,077,811
Sales Revenue, Net | Product Concentration Risk
Product Information [Line Items]
Percentage of consolidated net sales	100.00%	100.00%	100.00%	100.00%
Eliminations
Product Information [Line Items]
Net sales	$ (1,973)	$ (3,031)	$ (5,205)	$ (10,827)
Transportation Solutions
Product Information [Line Items]
Net sales	441,258	306,183	1,186,909	948,270
Transportation Solutions | Operating Segments
Product Information [Line Items]
Net sales	442,636	307,357	1,190,173	954,149
Transportation Solutions | Eliminations
Product Information [Line Items]
Net sales	1,378	1,174	3,264	5,879
Parts & Service
Product Information [Line Items]
Net sales	41,308	45,401	137,082	129,541
Parts & Service | Operating Segments
Product Information [Line Items]
Net sales	41,903	47,258	139,023	134,489
Parts & Service | Eliminations
Product Information [Line Items]
Net sales	595	1,857	1,941	4,948
New trailers
Product Information [Line Items]
Net sales	$ 375,430	$ 253,064	$ 966,193	$ 781,205
New trailers | Sales Revenue, Net | Product Concentration Risk
Product Information [Line Items]
Percentage of consolidated net sales	77.80%	72.00%	73.00%	72.50%
New trailers | Eliminations
Product Information [Line Items]
Net sales	$ 0	$ (444)	$ 0	$ (3,390)
New trailers | Transportation Solutions | Operating Segments
Product Information [Line Items]
Net sales	375,430	251,998	966,193	781,497
New trailers | Parts & Service | Operating Segments
Product Information [Line Items]
Net sales	0	1,510	0	3,098
Used trailers
Product Information [Line Items]
Net sales	$ 465	$ 1,961	$ 1,855	$ 7,085
Used trailers | Sales Revenue, Net | Product Concentration Risk
Product Information [Line Items]
Percentage of consolidated net sales	0.10%	0.60%	0.10%	0.70%
Used trailers | Eliminations
Product Information [Line Items]
Net sales	$ 0	$ 0	$ 0	$ 0
Used trailers | Transportation Solutions | Operating Segments
Product Information [Line Items]
Net sales	0	505	165	2,979
Used trailers | Parts & Service | Operating Segments
Product Information [Line Items]
Net sales	465	1,456	1,690	4,106
Components, parts and service
Product Information [Line Items]
Net sales	$ 30,001	$ 26,782	$ 96,542	$ 85,063
Components, parts and service | Sales Revenue, Net | Product Concentration Risk
Product Information [Line Items]
Percentage of consolidated net sales	6.20%	7.60%	7.30%	7.90%
Components, parts and service | Eliminations
Product Information [Line Items]
Net sales	$ (1,973)	$ (2,587)	$ (5,205)	$ (7,437)
Components, parts and service | Transportation Solutions | Operating Segments
Product Information [Line Items]
Net sales	0	0	0	0
Components, parts and service | Parts & Service | Operating Segments
Product Information [Line Items]
Net sales	31,974	29,369	101,747	92,500
Equipment and other
Product Information [Line Items]
Net sales	$ 76,670	$ 69,777	$ 259,401	$ 204,458
Equipment and other | Sales Revenue, Net | Product Concentration Risk
Product Information [Line Items]
Percentage of consolidated net sales	15.90%	19.80%	19.60%	19.00%
Equipment and other | Eliminations
Product Information [Line Items]
Net sales	$ 0	$ 0	$ 0	$ 0
Equipment and other | Transportation Solutions | Operating Segments
Product Information [Line Items]
Net sales	67,206	54,854	223,815	169,673
Equipment and other | Parts & Service | Operating Segments
Product Information [Line Items]
Net sales	$ 9,464	$ 14,923	$ 35,586	$ 34,785