Consolidated Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue Equipment [Member]
Operating expenses (income):
Gain on disposition of assets	$ (3,325)	$ (1,895)	$ (7,462)	$ (4,843)
Facility [Member]
Operating expenses (income):
Gain on disposition of assets				(3,712)
Operating revenue	170,464	171,346	498,483	496,221
Salaries, wages and benefits	57,090	55,129	168,116	154,901
Purchased transportation	27,775	30,756	81,997	88,343
Fuel and fuel taxes	24,845	26,556	68,405	81,313
Supplies and maintenance	11,618	11,351	33,025	32,735
Depreciation	20,790	19,331	61,205	55,469
Operating taxes and licenses	2,297	2,295	6,732	6,185
Insurance and claims	8,194	7,105	23,245	21,973
Communications and utilities	1,584	1,431	4,701	4,347
Gain on disposition of assets				(3,712)
Other	4,727	4,933	14,749	13,684
Total operating expenses	155,595	156,992	454,713	450,395
Operating income	14,869	14,354	43,770	45,826
Other	342	126	794	147
Income before income taxes	14,527	14,228	42,976	45,679
Provision for income taxes	6,090	5,818	17,815	18,724
Net income	$ 8,437	$ 8,410	$ 25,161	$ 26,955
Basic earnings per common share (in dollars per share)	$ 0.26	$ 0.25	$ 0.77	$ 0.80
Diluted earnings per common share (in dollars per share)	0.26	0.25	0.77	0.80
Dividends declared per common share (in dollars per share)	$ 0.025	$ 0.025	$ 0.075	$ 0.075