Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements of Operations [Abstract]
Operating revenue	$ 850,470	$ 736,185	$ 1,609,359	$ 1,391,015
Operating expenses:
Salaries, wages and employee benefits	202,556	186,918	398,032	364,721
Operating supplies and expenses	58,766	54,221	115,870	102,051
Fuel	168,537	115,494	318,818	221,576
Purchased transportation	223,680	197,789	417,717	373,491
Rental expense	19,224	19,493	37,213	38,396
Insurance and claims	27,876	29,479	50,601	49,686
Depreciation and amortization of property and equipment	51,553	48,403	101,911	108,422
Amortization of intangibles	4,617	5,199	9,344	10,677
Impairments				1,274
Gain on disposal of property and equipment	(700)	(1,757)	(2,955)	(3,205)
Communication and utilities	6,335	6,132	12,795	12,554
Operating taxes and licenses	15,459	13,625	30,717	26,990
Total operating expenses	777,903	674,996	1,490,063	1,306,633
Operating income	72,567	61,189	119,296	84,382
Other (income) expenses:
Interest expense	36,631	62,768	74,132	125,364
Derivative interest expense	4,003	18,292	8,683	42,006
Interest income	(471)	(283)	(938)	(503)
Other	(664)	(1,469)	(1,175)	(1,840)
Total other (income) expenses, net	39,499	79,308	80,702	165,027
Income (loss) before income taxes	33,068	(18,119)	38,594	(80,645)
Income tax expense (benefit)	13,485	4,960	15,806	(4,565)
Net income (loss)	$ 19,583	$ (23,079)	$ 22,788	$ (76,080)
Basic earnings (loss) per share	$ 0.14	$ (0.38)	$ 0.16	$ (1.27)
Diluted earnings (loss) per share	$ 0.14	$ (0.38)	$ 0.16	$ (1.27)
Shares used in per share calculations
Basic	139,479	60,117	138,807	60,117
Diluted	140,716	60,117	139,812	60,117