Statement of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash and cash equivalents, at beginning of period	$ 484,502	$ 429,784
Net income	66,560	56,902
Depreciation and amortization, net of accretion	120,223	112,774
Non-cash compensation and employee benefits	12,182	18,275
Increase in deferred income taxes	18,708	26,911
Provision for uncollectible accounts	1,402	5,334
Loss (gain) from sale of property and equipment	(5,375)	(7,062)
Receivables	(119,659)	(37,987)
Prepaid expense	(2,946)	4,797
Accounts payable	34,658	16,793
Accrued variable compensation	(6,307)	(33,902)
Accrued liabilities, excluding accrued variable compensation and employee benefits	32,962	29,570
Self-insurance accruals	5,617	(3,859)
Accrued income taxes	3,164	(8,358)
Employee benefits	(39,132)	(48,286)
Other	(412)	3,880
Net cash provided by operating activities	121,645	135,782
Capital expenditures	(123,366)	(129,273)
Software expenditures	(5,613)	(3,246)
Proceeds from sales of property and equipment	22,391	9,965
Proceeds from sales of marketable securities	0	3,200
Net cash used in investing activities	(106,588)	(119,354)
Payment of capital leases	(6,141)	(6,373)
Net proceeds from (repayment of) short-term borrowings	801	(4,698)
Payments of Debt Issuance Costs	0	(543)
Proceeds from exercise of stock options	13,573	8,987
Excess tax benefit from share-based compensation	2,413	1,057
Payments of common dividends	(11,413)	(11,255)
Net cash used in financing activities	(767)	(12,825)
Increase in cash and cash equivalents	14,290	3,603
Cash and Cash Equivalents, at end of period	498,792	433,387
Cash paid for income taxes, net	19,169	3,136
Cash paid for interest	26,232	26,516
Property, plant and equipment acquired through partial non-monetary exchanges	936	16,872
Property, plant and equipment acquired through capital leases	$ 7,233	$ 0