Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
ASSETS
Cash and cash equivalents	$ 433,387	$ 429,784
Marketable securities	0	3,200
Trade accounts receivable, net	601,958	567,097
Other accounts receivable	56,276	43,912
Operating supplies, at lower of average cost or market	25,199	23,180
Prepaid expenses	49,525	49,681
Deferred income taxes	15,618	34,520
Total Current Assets	1,181,963	1,151,374
Property, Plant and Equipment
Land	195,557	195,737
Buildings and leasehold improvements	846,729	840,966
Revenue equipment	1,761,947	1,746,816
Other equipment	331,065	329,730
Total Property, Plant and Equipment	3,135,298	3,113,249
Accumulated depreciation	(1,546,217)	(1,526,648)
Net Property, Plant and Equipment	1,589,081	1,586,601
Other Assets
Deferred charges and other assets	33,308	33,963
Capitalized software, net	19,979	20,365
Employee benefits	11,649	10,951
Intangible assets, net	9,818	10,997
Goodwill	337,943	338,164
Total Noncurrent Assets	412,697	414,440
Total Assets	3,183,741	3,152,415
LIABILITIES AND SHAREHOLDERS' EQUITY
Accounts payable	353,828	330,665
Accrued liabilities	231,204	253,209
Self-insurance accruals	105,708	100,828
Short-term borrowings	2,285	6,982
Current maturities of long-term debt and capital leases	14,950	16,008
Total Current Liabilities	707,975	707,692
Long-Term Liabilities
Long-term debt	719,085	719,016
Long-term obligations under capital leases	25,040	30,355
Self-insurance accruals	141,348	143,735
Employee benefits	556,587	603,619
Other liabilities and deferred credits	41,247	32,201
Deferred income taxes	92,722	77,412
Total Liabilities	2,284,004	2,314,030
Commitments and Contingencies (Notes 8 and 10)
Shareholders' Equity
Common stock, $0.625 par value; authorized 100,000,000 shares; issued 64,162,795 and 63,565,453 shares, respectively	40,080	39,701
Additional paid-in capital, common stock	631,809	614,334
Retained earnings	1,006,935	966,939
Cost of repurchased common stock (7,667,543 and 7,583,471 shares, respectively)	(328,988)	(326,128)
Accumulated other comprehensive loss	(450,099)	(456,461)
Total Shareholders' Equity	899,737	838,385
Total Liabilities and Shareholders' Equity	$ 3,183,741	$ 3,152,415