Consolidated Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenue Equipment [Member]
Operating expenses (income):
Gain on disposition of assets	$ (2,703)	$ (1,787)	$ (4,137)	$ (2,948)
Facility [Member]
Operating expenses (income):
Gain on disposition of assets				(3,712)
Operating revenue	166,090	163,588	328,019	324,875
Salaries, wages and benefits	56,196	50,964	111,026	99,772
Purchased transportation	26,187	28,083	54,222	57,587
Fuel and fuel taxes	23,930	28,281	43,560	54,757
Supplies and maintenance	10,908	10,942	21,407	21,384
Depreciation	20,368	18,311	40,415	36,138
Operating taxes and licenses	2,250	2,014	4,435	3,890
Insurance and claims	7,696	6,778	15,051	14,868
Communications and utilities	1,497	1,388	3,117	2,916
Gain on disposition of assets				(3,712)
Other	4,985	4,453	10,022	8,751
Total operating expenses	151,314	149,427	299,118	293,403
Operating income	14,776	14,161	28,901	31,472
Other	237	6	452	21
Income before income taxes	14,539	14,155	28,449	31,451
Provision for income taxes	6,008	5,798	11,725	12,906
Net income	$ 8,531	$ 8,357	$ 16,724	$ 18,545
Basic earnings per common share (in dollars per share)	$ 0.26	$ 0.25	$ 0.52	$ 0.55
Diluted earnings per common share (in dollars per share)	0.26	0.25	0.51	0.55
Dividends declared per common share (in dollars per share)	$ 0.025	$ 0.025	$ 0.05	$ 0.05