Statements Of Consolidated Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Statement [Abstract]
Revenues	$ 1,336,164	$ 1,366,161
Costs and Expenses
Salaries, wages and employee benefits	517,841	522,470
Purchased transportation	348,523	368,051
Other operating expenses	157,697	136,515
Fuel and fuel-related taxes	137,412	143,831
Depreciation and amortization	55,928	51,842
Rents and leases	29,850	28,700
Maintenance	29,332	31,910
Purchased labor	27,982	27,152
Total Costs and Expenses	1,304,565	1,310,471
Operating Income	31,599	55,690
Other Income (Expense)
Investment income	164	235
Interest expense	(13,505)	(13,794)
Miscellaneous, net	(1,483)	(709)
Total Other Expense	(14,824)	(14,268)
Income before Income Tax Provision	16,775	41,422
Income Tax Provision	2,770	15,776
Net Income	$ 14,005	$ 25,646
Weighted-Average Common Shares Outstanding
Basic	56,096,637	55,703,722
Diluted	56,731,972	56,257,783
Earnings per Common Share
Basic	$ 0.25	$ 0.46
Diluted	$ 0.25	$ 0.46