Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments			2
Revenues
Total Operating Revenue	$ 428,503	$ 460,227	$ 1,257,728	$ 1,335,693
Operating Income
Total Operating Income (Loss)	3,282	22,892	24,707	57,764
Truckload Segment [Member]
Revenues
Total Operating Revenue	382,467	395,167	1,125,991	1,157,731
Operating Income
Total Operating Income (Loss)	3,345	19,857	20,689	50,950
Brokerage Segment [Member]
Revenues
Total Operating Revenue	46,036	65,060	131,737	177,962
Operating Income
Total Operating Income (Loss)	$ (63)	$ 3,035	$ 4,018	$ 6,814