Consolidated Statements Of Income (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements Of Income
Operating revenues	$ 515,897	$ 463,469	$ 985,326	$ 888,544
Operating expenses:
Salaries, wages and benefits	135,265	134,303	268,128	262,637
Fuel	110,502	78,452	208,433	152,333
Supplies and maintenance	43,085	39,012	84,274	76,688
Taxes and licenses	23,414	23,560	46,440	47,017
Insurance and claims	16,531	18,869	34,591	35,707
Depreciation	39,246	37,471	78,964	75,756
Rent and purchased transportation	98,605	91,881	187,102	176,566
Communications and utilities	3,843	3,494	7,766	7,243
Other	(1,361)	881	(4,581)	787
Total operating expenses	469,130	427,923	911,117	834,734
Operating income	46,767	35,546	74,209	53,810
Other expense (income):
Interest expense	10	3	38	12
Interest income	(345)	(355)	(690)	(692)
Other	263	(33)	289	(44)
Total other expense (income)	(72)	(385)	(363)	(724)
Income before income taxes	46,839	35,931	74,572	54,534
Income taxes	19,321	15,001	30,761	22,768
Net income	$ 27,518	$ 20,930	$ 43,811	$ 31,766
Earnings per share:
Basic	$ 0.38	$ 0.29	$ 0.60	$ 0.44
Diluted	$ 0.38	$ 0.29	$ 0.60	$ 0.44
Dividends declared per share	$ 0.050	$ 0.050	$ 0.100	$ 0.100
Weighted-average common shares outstanding:
Basic	72,794	72,280	72,749	72,141
Diluted	73,239	72,767	73,190	72,658