Revenue Recognition - Disaggregation of Revenue by Type (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 133,622	$ 135,381	$ 267,596	$ 260,394
Freight
Disaggregation of Revenue [Line Items]
Revenues	115,153	117,549	230,994	224,831
Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	16,901	16,274	32,341	31,008
Accessorial
Disaggregation of Revenue [Line Items]
Revenues	1,568	1,558	4,261	4,555
Trucking
Disaggregation of Revenue [Line Items]
Revenues	96,069	85,569	190,609	164,302
USAT Logistics
Disaggregation of Revenue [Line Items]
Revenues	37,553	49,812	76,987	96,092
Operating Segments | Trucking
Disaggregation of Revenue [Line Items]
Revenues	96,476	85,685	191,378	164,531
Operating Segments | Trucking | Freight
Disaggregation of Revenue [Line Items]
Revenues	82,664	73,029	164,086	139,934
Operating Segments | Trucking | Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	13,034	12,135	24,799	23,322
Operating Segments | Trucking | Accessorial
Disaggregation of Revenue [Line Items]
Revenues	778	521	2,493	1,275
Operating Segments | USAT Logistics
Disaggregation of Revenue [Line Items]
Revenues	39,575	50,616	81,025	97,391
Operating Segments | USAT Logistics | Freight
Disaggregation of Revenue [Line Items]
Revenues	34,698	45,371	71,328	86,308
Operating Segments | USAT Logistics | Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	4,087	4,208	7,929	7,803
Operating Segments | USAT Logistics | Accessorial
Disaggregation of Revenue [Line Items]
Revenues	790	1,037	1,768	3,280
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(2,429)	(920)	(4,807)	(1,528)
Intersegment Eliminations | Freight
Disaggregation of Revenue [Line Items]
Revenues	(2,209)	(851)	(4,420)	(1,411)
Intersegment Eliminations | Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	(220)	(69)	(387)	(117)
Intersegment Eliminations | Accessorial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations | Trucking
Disaggregation of Revenue [Line Items]
Revenues	(407)	(116)	(769)	(229)
Intersegment Eliminations | USAT Logistics
Disaggregation of Revenue [Line Items]
Revenues	$ (2,022)	$ (804)	$ (4,038)	$ (1,299)