Statements Of Consolidated Cash Flows (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Statements Of Consolidated Cash Flows
Cash and Cash Equivalents, Beginning of Period	$ 421,420	$ 476,575
Operating Activities
Net income	36,344	9,826
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization, net of accretion	100,364	90,349
Non-cash compensation and employee benefits	12,207	10,174
Increase in deferred income taxes	26,224	2,574
Provision for uncollectible accounts	3,159	2,924
Loss from impairment of intangible assets		2,767
Loss (Gain) from sales of property and equipment, net	(1,632)	783
Changes in assets and liabilities:
Receivables	(96,076)	(121,567)
Prepaid expenses	2,055	(3,265)
Accounts payable	63,386	71,243
Accrued variable compensation	(1,506)	(591)
Accrued liabilities, excluding accrued variable compensation and employee benefits	25,000	16,635
Self-insurance accruals	(14,858)	22,019
Accrued income taxes	29,942	(6,388)
Employee benefits	1,389	13,269
Deferred charges and credits	1,699	(2,300)
Other	(1,751)	(2,114)
Net Cash Provided by Operating Activities	185,946	106,338
Investing Activities
Capital expenditures	(138,834)	(88,351)
Software expenditures	(3,854)	(4,700)
Proceeds from sales of property and equipment	19,891	2,436
Purchases of marketable securities		(49,260)
Proceeds from sales of marketable securities	300	10,300
Net Cash Used in Investing Activities	(122,497)	(129,575)
Financing Activities
Repayment of long-term debt and capital leases	(9,272)	(204,316)
Net proceeds from short-term borrowings	245	6,035
Proceeds from issuance of common stock		143,325
Proceeds from exercise of stock options	4,087	1,148
Excess tax benefit from stock-option exercises	544	146
Payments of common dividends	(11,060)	(9,924)
Net Cash Used in Financing Activities	(15,456)	(63,586)
Increase (Decrease) in Cash and Cash Equivalents	47,993	(86,823)
Cash and Cash Equivalents, End of Period	469,413	389,752
Supplemental Disclosures
Cash paid (refunded) for income taxes, net	(28,881)	16,463
Cash paid for interest, net of amounts capitalized	27,421	35,560
Non-cash Financing Activities
Capital lease incurred to acquire revenue equipment		35,104
Repurchased common stock issued under defined contribution plan	$ 17,307	$ 17,945