Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 402,846	$ 438,010
Marketable securities	16,215	13,255
Trade accounts receivable, net	644,881	577,522
Other accounts receivable	47,797	43,849
Operating supplies, at lower of average cost or market	24,029	22,822
Prepaid expenses	61,851	48,369
Deferred income taxes	37,135	46,563
Total Current Assets	1,234,754	1,190,390
Property, Plant and Equipment
Land	191,515	194,078
Buildings and leasehold improvements	827,171	827,910
Revenue equipment	1,667,117	1,613,806
Other equipment	322,120	318,313
Total Property, Plant and Equipment	3,007,923	2,954,107
Accumulated depreciation	(1,482,285)	(1,458,074)
Net Property, Plant and Equipment	1,525,638	1,496,033
Other Assets
Deferred charges and other assets	37,139	36,743
Capitalized software, net	18,902	19,829
Marketable securities	5,394	5,354
Intangible assets, net	13,150	13,951
Goodwill	337,951	337,716
Total Noncurrent Assets	412,536	413,593
Total Assets	3,172,928	3,100,016
LIABILITIES AND SHAREHOLDERS' EQUITY
Accounts payable	385,855	345,489
Accrued liabilities	242,850	235,146
Self-insurance accruals	104,544	104,328
Short-term borrowings	15,804	14,481
Current maturities of long-term debt and capital leases	23,086	24,026
Total Current Liabilities	772,139	723,470
Long-Term Liabilities
Long-term debt	718,368	718,336
Long-term obligations under capital leases	48,026	51,902
Self-insurance accruals	159,682	158,889
Employee benefits	601,810	610,850
Other liabilities and deferred credits	41,422	39,120
Deferred income taxes	46,202	38,195
Total Liabilities	2,387,649	2,340,762
Commitments and Contingencies (Note 8)
Shareholders' Equity
Common stock, $0.625 par value; authorized 100,000,000 shares; issued 63,363,118 and 63,065,931 shares, respectively	39,583	39,394
Additional paid-in capital, common stock	601,256	595,992
Retained earnings	904,821	884,758
Cost of repurchased common stock (7,569,160 and 7,468,869 shares, respectively)	(325,696)	(322,454)
Accumulated other comprehensive loss	(434,685)	(438,436)
Total Shareholders' Equity	785,279	759,254
Total Liabilities and Shareholders' Equity	$ 3,172,928	$ 3,100,016