Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets
Cash and cash equivalents	$ 429,784	$ 438,010
Marketable securities	3,200	13,255
Trade accounts receivable, net	567,097	577,522
Other accounts receivable	43,912	43,849
Operating supplies, at lower of average cost or market	23,180	22,822
Prepaid expenses	49,681	48,369
Deferred income taxes	34,520	46,563
Total Current Assets	1,151,374	1,190,390
Property, Plant and Equipment [Abstract]
Land	195,737	194,078
Buildings and leasehold improvements	840,966	827,910
Revenue equipment	1,746,816	1,613,806
Other equipment	329,730	318,313
Total Property, Plant and Equipment	3,113,249	2,954,107
Accumulated depreciation	(1,526,648)	(1,458,074)
Net Property, Plant and Equipment	1,586,601	1,496,033
Other Assets
Deferred charges and other assets	33,963	36,743
Capitalized software, net	20,365	19,829
Other marketable securities	0	5,354
Intangible assets, net	10,997	13,951
Goodwill	338,164	337,716
Total Noncurrent Assets	403,489	413,593
Total Assets	3,141,464	3,100,016
Liabilities and Shareholders' Equity
Accounts payable	330,665	345,489
Accrued liabilities	253,209	235,146
Self-insurance accruals	100,828	104,328
Short-term borrowings	6,982	14,481
Current maturities of long-term debt and capital leases	16,008	24,026
Total Current Liabilities	707,692	723,470
Long-Term Liabilities
Long-term debt	719,016	718,336
Long-term obligations under capital leases	30,355	51,902
Self-insurance accruals	143,735	158,889
Employee benefits	592,668	610,850
Other liabilities and deferred credits	32,201	39,120
Deferred income taxes	77,412	38,195
Total Liabilities	2,303,079	2,340,762
Commitments and Contingencies (Notes 6, 7, 8 and 12)
Shareholders' Equity
Common stock, $.625 par value; authorized 100,000,000 shares; issued 63,565,453 and 63,065,931 shares, respectively	39,701	39,394
Additional paid-in capital, common stock	614,334	595,992
Retained earnings	966,939	884,758
Cost of repurchased common stock (7,583,471 and 7,468,869 shares, respectively)	(326,128)	(322,454)
Accumulated Other Comprehensive Loss	(456,461)	(438,436)
Total Shareholders' Equity	838,385	759,254
Total Liabilities and Shareholders' Equity	$ 3,141,464	$ 3,100,016