Consolidated Statements Of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating revenues	$ 551,961	$ 511,728	$ 1,586,103	$ 1,511,263
Operating expenses:
Salaries, wages and benefits	149,206	137,834	428,425	406,175
Fuel	86,820	92,890	270,026	279,874
Supplies and maintenance	48,527	46,538	140,268	133,600
Taxes and licenses	21,420	21,548	63,563	64,758
Insurance and claims	19,789	16,714	59,175	53,835
Depreciation	44,182	42,612	131,878	127,310
Rent and purchased transportation	133,893	117,651	373,778	339,029
Communications and utilities	3,689	3,754	10,597	10,083
Other	2,745	(396)	932	(7,038)
Total operating expenses	510,271	479,145	1,478,642	1,407,626
Operating income	41,690	32,583	107,461	103,637
Other expense (income):
Interest expense	140	101	370	336
Interest income	(614)	(589)	(1,929)	(1,629)
Other	43	(35)	2	(127)
Total other income	(431)	(523)	(1,557)	(1,420)
Income before income taxes	42,121	33,106	109,018	105,057
Income taxes	16,151	11,847	43,077	40,447
Net income	$ 25,970	$ 21,259	$ 65,941	$ 64,610
Earnings per share:
Basic	$ 0.36	$ 0.29	$ 0.91	$ 0.89
Diluted	$ 0.36	$ 0.29	$ 0.91	$ 0.88
Dividends declared per share	$ 0.050	$ 0.050	$ 0.150	$ 0.150
Weighted-average common shares outstanding:
Basic	71,837	72,621	72,198	72,965
Diluted	72,364	73,216	72,706	73,530