Statements Of Consolidated Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Cash Flows [Abstract]
Cash and Cash Equivalents, Beginning of Period	$ 429,784	$ 438,010	$ 421,420
Net Cash Provided by (Used In) Operating Activities [Abstract]
Net Income	99,153	104,546	88,443
Adjustments to Reconcile Net Income to Cash Provided by Operating Activities [Abstract]
Depreciation and amortization, net of accretion	229,236	215,202	201,638
Non-cash compensation and employee benefits	38,496	33,180	22,050
Increase in deferred income taxes	57,423	63,091	52,160
Provision for uncollectible accounts	6,908	6,358	6,761
Gain from purchase-price adjustment	0	0	(10,000)
Gain from sales of property, equipment and investment, net	(5,720)	(8,649)	(7,120)
Increase (Decrease) in Operating Capital [Abstract]
Receivables	(12,869)	7,076	(42,315)
Prepaid expenses	21	(1,312)	(1,024)
Accounts payable	25,972	(14,824)	41,313
Accrued variable compensation	(17,140)	1,201	22,439
Accrued liabilities, excluding accrued variable compensation and employee benefits	11,572	1,988	3,808
Self-insurance accruals	(3,661)	(18,654)	(11,951)
Accrued income taxes	(4,846)	(2,316)	34,362
Employee benefits	(82,507)	(67,291)	(52,713)
Other	5,946	(8,185)	(3,141)
Net Cash Provided by Operating Activities	347,984	311,411	344,710
Net Cash Used in Investing Activities [Abstract]
Capital expenditures	(281,943)	(293,135)	(288,994)
Software expenditures	(7,398)	(8,963)	(8,667)
Proceeds from sales of property and equipment	14,202	20,840	13,213
Proceeds from purchase-price adjustment	0	0	10,000
Purchases of marketable securities	0	(8,200)	(13,480)
Proceeds from sales of marketable securities	3,200	23,613	900
Net Cash Used in Investing Activities	(271,939)	(265,845)	(287,028)
Net Cash Used in Financing Activities [Abstract]
Payment of capital leases	(16,068)	(29,015)	(19,811)
Net repayments of short-term borrowings	(5,383)	(7,621)	(4,691)
Payment of debt issuance costs	(543)	0	(661)
Proceeds from exercise of stock options	20,777	3,560	5,532
Excess tax benefit from share-based compensation	2,510	1,641	716
Payments of common dividends	(22,620)	(22,357)	(22,177)
Net Cash Used in Financing Activities	(21,327)	(53,792)	(41,092)
Increase (Decrease) in Cash and Cash Equivalents	54,718	(8,226)	16,590
Cash and Cash Equivalents, End of Period	484,502	429,784	438,010
Supplemental Disclosure
Cash paid (refunded) for income taxes, net	(21)	6,163	(28,740)
Cash paid for interest, net of amounts capitalized	$ 52,809	$ 53,806	$ 54,676