Condensed Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Operating revenue:
Total operating revenue	$ 135,749	$ 121,522	$ 388,143	$ 350,629
Operating expenses:
Total purchased transportation	56,089	51,177	160,621	146,368
Salaries, wages and employee benefits	33,402	31,845	95,336	95,682
Operating leases	6,672	6,508	20,083	19,388
Depreciation and amortization	5,429	5,228	15,734	15,283
Insurance and claims	2,120	1,546	6,140	5,983
Fuel expense	2,406	1,949	7,357	6,051
Other operating expenses	9,311	7,764	29,390	26,813
Total operating expenses	115,429	106,017	334,661	315,568
Income from operations	20,320	15,505	53,482	35,061
Other income (expense):
Interest expense	(131)	(191)	(468)	(557)
Other, net	10	26	57	38
Total other expense	(121)	(165)	(411)	(519)
Income before income taxes	20,199	15,340	53,071	34,542
Income taxes	7,287	6,452	20,321	14,323
Net income	$ 12,912	$ 8,888	$ 32,750	$ 20,219
Net income per share:
Basic (in dollars per share)	$ 0.44	$ 0.31	$ 1.12	$ 0.70
Diluted (in dollars per share)	$ 0.44	$ 0.31	$ 1.11	$ 0.69
Weighted average shares outstanding:
Basic (in shares)	29,237	29,000	29,236	28,975
Diluted (in shares)	29,552	29,129	29,591	29,101
Dividends per share (in dollars per share)	$ 0.07	$ 0.07	$ 0.21	$ 0.21