Related Party (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Due to Related Parties, Current	$ 0		$ 0		$ 100
Operating Leases, Rent Expense	300	$ 900	800	$ 2,100
related party payment for terminal purchase	0	4,875	0	4,875
Costs and Expenses, Related Party	5,277	19,456	6,719	16,432
Related Party
Related Party Transaction [Line Items]
Payments for tractor purchase	4,300	22,795	4,300	24,895
Receipts for tractor sales	0	(11,041)	0	(19,567)
Receipts for trailer sales			(108)	0
Operating Leases, Rent Expense	265	799	813	1,884
Payments for parts and services	246	1,065	783	2,426
Terminal Facilities
Related Party Transaction [Line Items]
Operating Leases, Rent Expense	500	1,000	1,100	2,100
Terminal Facilities | Related Party
Related Party Transaction [Line Items]
Operating Leases, Rent Expense	$ 466	$ 963	$ 900	$ 1,919