Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
ASSETS
Cash and cash equivalents	$ 404,531	$ 429,784
Marketable securities	0	3,200
Trade accounts receivable, net	615,286	567,097
Other accounts receivable	56,226	43,912
Operating supplies, at lower of average cost or market	24,378	23,180
Prepaid expenses	63,629	49,681
Deferred income taxes	27,237	34,520
Total Current Assets	1,191,287	1,151,374
Property, Plant and Equipment
Land	195,737	195,737
Buildings and leasehold improvements	844,857	840,966
Revenue equipment	1,732,586	1,746,816
Other equipment	331,729	329,730
Total Property, Plant and Equipment	3,104,909	3,113,249
Accumulated depreciation	(1,538,409)	(1,526,648)
Net Property, Plant and Equipment	1,566,500	1,586,601
Other Assets
Deferred charges and other assets	35,168	33,963
Capitalized software, net	20,349	20,365
Employee benefits	11,301	10,951
Intangible assets, net	10,408	10,997
Goodwill	338,029	338,164
Total Noncurrent Assets	415,255	414,440
Total Assets	3,173,042	3,152,415
LIABILITIES AND SHAREHOLDERS' EQUITY
Accounts payable	366,652	330,665
Accrued liabilities	228,537	253,209
Self-insurance accruals	105,862	100,828
Short-term borrowings	2,830	6,982
Current maturities of long-term debt and capital leases	15,480	16,008
Total Current Liabilities	719,361	707,692
Long-Term Liabilities
Long-term debt	719,050	719,016
Long-term obligations under capital leases	27,710	30,355
Self-insurance accruals	143,884	143,735
Employee benefits	589,286	603,619
Other liabilities and deferred credits	37,857	32,201
Deferred income taxes	77,521	77,412
Total Liabilities	2,314,669	2,314,030
Commitments and Contingencies (Note 8)
Shareholders' Equity
Common stock, $0.625 par value; authorized 100,000,000 shares; issued 63,946,222 and 63,565,453 shares, respectively	39,942	39,701
Additional paid-in capital, common stock	624,244	614,334
Retained earnings	975,327	966,939
Cost of repurchased common stock (7,644,407 and 7,583,471 shares, respectively)	(328,221)	(326,128)
Accumulated other comprehensive loss	(452,919)	(456,461)
Total Shareholders' Equity	858,373	838,385
Total Liabilities and Shareholders' Equity	$ 3,173,042	$ 3,152,415