Revenue Recognition - Disaggregation of Revenue by Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 133,974	$ 125,013
Freight
Disaggregation of Revenue [Line Items]
Revenues	115,843	107,282
Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	15,440	14,734
Accessorial
Disaggregation of Revenue [Line Items]
Revenues	2,691	2,997
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(2,377)	(608)
Intersegment Eliminations | Freight
Disaggregation of Revenue [Line Items]
Revenues	(2,210)	(608)
Intersegment Eliminations | Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	(167)	0
Intersegment Eliminations | Accessorial
Disaggregation of Revenue [Line Items]
Revenues	0	0
Operating Segments | Trucking
Disaggregation of Revenue [Line Items]
Revenues	94,902	78,846
Operating Segments | Trucking | Freight
Disaggregation of Revenue [Line Items]
Revenues	81,423	66,917
Operating Segments | Trucking | Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	11,765	11,175
Operating Segments | Trucking | Accessorial
Disaggregation of Revenue [Line Items]
Revenues	1,714	754
Operating Segments | USAT Logistics
Disaggregation of Revenue [Line Items]
Revenues	41,449	46,775
Operating Segments | USAT Logistics | Freight
Disaggregation of Revenue [Line Items]
Revenues	36,630	40,973
Operating Segments | USAT Logistics | Fuel Surcharge
Disaggregation of Revenue [Line Items]
Revenues	3,842	3,559
Operating Segments | USAT Logistics | Accessorial
Disaggregation of Revenue [Line Items]
Revenues	$ 977	$ 2,243