REVENUE RECOGNITION - Disaggregation of Revenue by Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue
Revenues	$ 130,924	$ 132,583	$ 398,520	$ 392,977
Intersegment Eliminations
Disaggregation of Revenue
Revenues	(2,028)	(3,354)	(6,835)	(4,882)
Trucking
Disaggregation of Revenue
Revenues	93,354	85,529	283,963	249,831
Trucking | Operating Segments
Disaggregation of Revenue
Revenues	93,587	86,801	284,965	251,332
Trucking | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(233)	(1,272)	(1,002)	(1,501)
USAT Logistics
Disaggregation of Revenue
Revenues	37,570	47,054	114,557	143,146
USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	39,365	49,136	120,390	146,527
USAT Logistics | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(1,795)	(2,082)	(5,833)	(3,381)
Freight
Disaggregation of Revenue
Revenues	112,977	113,520	343,971	338,351
Freight | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(1,778)	(3,051)	(6,199)	(4,462)
Freight | Trucking | Operating Segments
Disaggregation of Revenue
Revenues	80,002	72,924	244,089	212,858
Freight | USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	34,753	43,647	106,081	129,955
Fuel surcharge
Disaggregation of Revenue
Revenues	16,015	15,982	48,357	46,990
Fuel surcharge | Intersegment Eliminations
Disaggregation of Revenue
Revenues	(250)	(303)	(636)	(420)
Fuel surcharge | Trucking | Operating Segments
Disaggregation of Revenue
Revenues	12,274	12,002	37,073	35,324
Fuel surcharge | USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	3,991	4,283	11,920	12,086
Accessorial
Disaggregation of Revenue
Revenues	1,932	3,081	6,192	7,636
Accessorial | Intersegment Eliminations
Disaggregation of Revenue
Revenues	0	0	0	0
Accessorial | Trucking | Operating Segments
Disaggregation of Revenue
Revenues	1,311	1,875	3,803	3,150
Accessorial | USAT Logistics | Operating Segments
Disaggregation of Revenue
Revenues	$ 621	$ 1,206	$ 2,389	$ 4,486