Consolidated Statements Of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating revenues	$ 542,120	$ 506,648	$ 1,034,142	$ 999,535
Operating expenses:
Salaries, wages and benefits	144,506	135,236	279,219	268,341
Fuel	92,131	90,191	183,206	186,984
Supplies and maintenance	45,887	43,934	91,741	87,062
Taxes and licenses	21,311	21,586	42,143	43,210
Insurance and claims	19,180	17,320	39,386	37,121
Depreciation	44,573	42,367	87,696	84,698
Rent and purchased transportation	128,239	115,060	239,885	221,378
Communications and utilities	3,409	3,187	6,908	6,329
Other	554	(4,594)	(1,813)	(6,642)
Total operating expenses	499,790	464,287	968,371	928,481
Operating income	42,330	42,361	65,771	71,054
Other expense (income):
Interest expense	136	91	230	235
Interest income	(660)	(535)	(1,315)	(1,040)
Other	(45)	(82)	(41)	(92)
Total other income	(569)	(526)	(1,126)	(897)
Income before income taxes	42,899	42,887	66,897	71,951
Income taxes	17,267	17,047	26,926	28,600
Net income	$ 25,632	$ 25,840	$ 39,971	$ 43,351
Earnings per share:
Basic	$ 0.36	$ 0.35	$ 0.55	$ 0.59
Diluted	$ 0.35	$ 0.35	$ 0.55	$ 0.59
Dividends declared per share	$ 0.050	$ 0.050	$ 0.100	$ 0.100
Weighted-average common shares outstanding:
Basic	72,091	73,022	72,382	73,140
Diluted	72,597	73,598	72,882	73,690