Statements of Consolidated Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash and Cash Equivalents, at Beginning of Period	$ 432,759	$ 484,502
Net income	21,792	12,893
Depreciation and amortization, net of accretion	60,048	59,409
Non-cash compensation and employee benefits	8,996	4,761
Increase in deferred income taxes	648	1,709
Provision for uncollectible accounts	344	439
Loss (gain) from sale of property and equipment	643	(1,211)
Receivables	(41,820)	(87,887)
Prepaid expense	(11,236)	(18,051)
Accounts payable	47,497	34,843
Accrued variable compensation	(44,931)	(26,787)
Accrued liabilities, excluding accrued variable compensation and employee benefits	39,008	35,301
Self-insurance accruals	(12,256)	13,546
Accrued income taxes	21,843	1,608
Employee benefits	(10,419)	(33,860)
Other	(11,281)	(1,256)
Net Cash Provided by (Used in) Operating Activities	68,876	(4,543)
Capital expenditures	(44,945)	(70,478)
Software expenditures	(4,018)	(2,637)
Proceeds from sales of property and equipment	3,025	5,842
Net cash used in investing activities	(45,938)	(67,273)
Payment of capital leases	(2,187)	(2,866)
Net proceeds from short-term borrowings	121	286
Proceeds from exercise of stock options	559	824
Excess tax benefit from share-based compensation	2,775	505
Payments of common dividends	(8,645)	(5,703)
Repurchases of common stock	(15,955)	0
Net Cash Used in Financing Activities	(23,332)	(6,954)
Decrease in Cash and Cash Equivalents	(394)	(78,770)
Cash and Cash Equivalents, at End of Period	432,365	405,732
Cash paid (refunded) for income taxes, net	(11,140)	2,554
Cash paid for interest	15,686	15,735
Property, plant and equipment acquired through increase in current liabilities	11,705	0
Repurchases of common stock included in current liabilities	1,323	0
Property, plant and equipment acquired through partial non-monetary exchanges	0	2,518
Property, plant and equipment acquired through capital leases	$ 0	$ 3,810