Consolidated Statements Of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating revenues	$ 492,887	$ 498,376
Operating expenses:
Salaries, wages and benefits	133,105	133,848
Fuel	96,793	102,937
Supplies and maintenance	43,128	41,837
Taxes and licenses	21,624	22,532
Insurance and claims	19,801	19,224
Depreciation	42,331	40,671
Rent and purchased transportation	106,318	100,510
Communications and utilities	3,142	3,819
Other	(2,048)	(2,404)
Total operating expenses	464,194	462,974
Operating income	28,693	35,402
Other expense (income):
Interest expense	144	142
Interest income	(505)	(422)
Other	(10)	(24)
Total other income	(371)	(304)
Income before income taxes	29,064	35,706
Income taxes	11,553	14,461
Net income	$ 17,511	$ 21,245
Earnings per share:
Basic	$ 0.24	$ 0.29
Diluted	$ 0.24	$ 0.29
Dividends declared per share	$ 0.050	$ 0.050
Weighted-average common shares outstanding:
Basic	73,260	72,854
Diluted	73,782	73,390