REVENUE RECOGNITION - Disaggregation of Revenue by Type (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
Disaggregation of Revenue
Revenues	$ 141,786	$ 130,924	$ 392,296	$ 398,520
Contract assets	1,900		1,900		$ 900
Intersegment Eliminations
Disaggregation of Revenue
Revenues	(7,656)	(2,028)	(14,332)	(6,835)
Trucking
Disaggregation of Revenue
Revenues	96,732	93,354	277,652	283,963
Trucking | Operating Segments
Disaggregation of Revenue
Revenues	97,383	93,587	280,005	284,965
Trucking | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(651)	(233)	(2,353)	(1,002)
USAT Logistics
Disaggregation of Revenue
Revenues	45,054	37,570	114,644	114,557
USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	52,059	39,365	126,623	120,390
USAT Logistics | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(7,005)	(1,795)	(11,979)	(5,833)
Freight
Disaggregation of Revenue
Revenues	128,160	112,977	348,130	343,971
Freight | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(7,493)	(1,778)	(13,648)	(6,199)
Freight | Trucking | Operating Segments
Disaggregation of Revenue
Revenues	87,505	80,002	246,922	244,089
Freight | USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	48,148	34,753	114,856	106,081
Fuel Surcharge
Disaggregation of Revenue
Revenues	10,249	16,015	34,794	48,357
Fuel Surcharge | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(163)	(250)	(684)	(636)
Fuel Surcharge | Trucking | Operating Segments
Disaggregation of Revenue
Revenues	7,847	12,274	27,218	37,073
Fuel Surcharge | USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	2,565	3,991	8,260	11,920
Accessorial
Disaggregation of Revenue
Revenues	3,377	1,932	9,372	6,192
Accessorial | Trucking | Operating Segments
Disaggregation of Revenue
Revenues	2,031	1,311	5,865	3,803
Accessorial | USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	$ 1,346	$ 621	$ 3,507	$ 2,389