DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue
Operating revenue	$ 551,138	$ 522,631
Freight
Disaggregation of Revenue
Operating revenue	493,889	451,176
Fuel Surcharge
Disaggregation of Revenue
Operating revenue	45,418	63,755
Accessorial
Disaggregation of Revenue
Operating revenue	11,831	7,700
Trucking
Disaggregation of Revenue
Operating revenue	381,589	375,657
USAT Logistics
Disaggregation of Revenue
Operating revenue	169,549	146,974
Operating Segments | Trucking
Disaggregation of Revenue
Operating revenue	384,256	377,093
Operating Segments | Trucking | Freight
Disaggregation of Revenue
Operating revenue	341,522	323,109
Operating Segments | Trucking | Fuel Surcharge
Disaggregation of Revenue
Operating revenue	35,049	49,059
Operating Segments | Trucking | Accessorial
Disaggregation of Revenue
Operating revenue	7,685	4,925
Operating Segments | USAT Logistics
Disaggregation of Revenue
Operating revenue	191,951	154,011
Operating Segments | USAT Logistics | Freight
Disaggregation of Revenue
Operating revenue	176,439	135,704
Operating Segments | USAT Logistics | Fuel Surcharge
Disaggregation of Revenue
Operating revenue	11,366	15,532
Operating Segments | USAT Logistics | Accessorial
Disaggregation of Revenue
Operating revenue	4,146	2,775
Intersegment Eliminations
Disaggregation of Revenue
Operating revenue	(25,069)	(8,473)
Intersegment Eliminations | Freight
Disaggregation of Revenue
Operating revenue	(24,072)	(7,637)
Intersegment Eliminations | Fuel Surcharge
Disaggregation of Revenue
Operating revenue	(997)	(836)
Intersegment Eliminations | Trucking
Disaggregation of Revenue
Operating revenue	(2,667)	(1,436)
Intersegment Eliminations | USAT Logistics
Disaggregation of Revenue
Operating revenue	$ (22,402)	$ (7,037)