Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Consolidated Statements of Operations [Abstract]
Operating revenue	$ 863,826	$ 758,281	$ 2,473,185	$ 2,149,296
Operating expenses:
Salaries, wages and employee benefits	197,046	187,299	595,078	552,020
Operating supplies and expenses	61,794	59,099	177,664	161,150
Fuel	159,719	116,899	478,537	338,475
Purchased transportation	234,743	198,910	652,460	572,401
Rental expense	23,685	19,187	60,898	57,583
Insurance and claims	21,252	22,898	71,853	72,584
Depreciation and amortization of property and equipment	51,058	48,027	152,969	156,449
Amortization of intangibles	4,509	4,955	13,853	15,632
Impairments				1,274
Gain on disposal of property and equipment	(2,946)	(1,808)	(5,901)	(5,013)
Communication and utilities	6,819	6,408	19,614	18,962
Operating taxes and licenses	16,450	14,307	47,167	41,297
Total operating expenses	774,129	676,181	2,264,192	1,982,814
Operating income	89,697	82,100	208,993	166,482
Other (income) expenses:
Interest expense	36,629	64,095	110,761	189,459
Derivative interest expense	3,384	16,963	12,067	58,969
Interest income	(562)	(297)	(1,500)	(800)
Other	(380)	(612)	(1,555)	(2,452)
Total other (income) expenses, net	39,071	80,149	119,773	245,176
Income (loss) before income taxes	50,626	1,951	89,220	(78,694)
Income tax expense (benefit)	19,676	2,970	35,482	(1,595)
Net income (loss)	$ 30,950	$ (1,019)	$ 53,738	$ (77,099)
Basic earnings (loss) per share	$ 0.22	$ (0.02)	$ 0.39	$ (1.28)
Diluted earnings (loss) per share	$ 0.22	$ (0.02)	$ 0.38	$ (1.28)
Shares used in per share calculations
Basic	139,498	60,117	139,039	60,117
Diluted	139,503	60,117	139,709	60,117