Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current Assets
Cash and cash equivalents	$ 478,120	$ 429,784
Marketable securities	0	3,200
Trade accounts receivable, net	597,896	567,097
Other accounts receivable	55,659	43,912
Operating supplies, at lower of average cost or market	25,010	23,180
Prepaid expenses and other current assets	42,720	49,681
Deferred income taxes	16,147	34,520
Total Current Assets	1,215,552	1,151,374
Property, Plant and Equipment
Land	194,539	195,737
Buildings and leasehold improvements	851,365	840,966
Revenue equipment	1,800,885	1,746,816
Other equipment	339,997	329,730
Total Property, Plant and Equipment	3,186,786	3,113,249
Accumulated depreciation	(1,572,515)	(1,526,648)
Net Property, Plant and Equipment	1,614,271	1,586,601
Other Assets
Deferred charges and other assets	32,572	33,963
Capitalized software, net	19,727	20,365
Employee benefits	11,999	10,951
Intangible assets, net	9,229	10,997
Goodwill	337,866	338,164
Total Noncurrent Assets	411,393	414,440
Total Assets	3,241,216	3,152,415
Current Liabilities
Accounts payable	360,987	330,665
Accrued liabilities	244,180	253,209
Self-insurance accruals	107,232	100,828
Short-term borrowings	2,047	6,982
Current maturities of capital leases	14,668	16,008
Total Current Liabilities	729,114	707,692
Long-Term Liabilities
Long-term debt	719,120	719,016
Long-term obligations under capital leases	23,693	30,355
Self-insurance accruals	144,484	143,735
Employee benefits	524,852	603,619
Other liabilities and deferred credits	41,009	32,201
Deferred income taxes	114,990	77,412
Total Liabilities	2,297,262	2,314,030
Commitments and Contingencies (Notes 8 and 10)
Shareholders' Equity
Common stock, $0.625 par value; authorized 100,000,000 shares; issued 64,559,832 and 63,565,453 shares, respectively	40,328	39,701
Additional paid-in capital, common stock	647,639	614,334
Retained earnings	1,031,777	966,939
Cost of repurchased common stock (7,668,921 and 7,583,471 shares, respectively)	(329,047)	(326,128)
Accumulated other comprehensive loss	(446,743)	(456,461)
Total Shareholders' Equity	943,954	838,385
Total Liabilities and Shareholders' Equity	$ 3,241,216	$ 3,152,415