CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
REVENUES	$ 2,337,413us-gaap_SalesRevenueNet	$ 1,861,489us-gaap_SalesRevenueNet	$ 1,945,023us-gaap_SalesRevenueNet
COSTS AND EXPENSES:
Cost of revenues (exclusive of items shown separately below)	1,493,082us-gaap_CostOfGoodsAndServicesSold	1,178,412us-gaap_CostOfGoodsAndServicesSold	1,105,886us-gaap_CostOfGoodsAndServicesSold
Selling, general and administrative expenses	198,076	185,165	175,749
Depreciation and amortization	230,813us-gaap_DepreciationAndAmortization	213,128us-gaap_DepreciationAndAmortization	214,899us-gaap_DepreciationAndAmortization
Loss on disposition of assets, net	15,472us-gaap_GainLossOnDispositionOfAssets	9,371us-gaap_GainLossOnDispositionOfAssets	6,099us-gaap_GainLossOnDispositionOfAssets
Operating profit	399,970us-gaap_OperatingIncomeLoss	275,413us-gaap_OperatingIncomeLoss	442,390us-gaap_OperatingIncomeLoss
Interest expense	(1,431)us-gaap_InterestExpense	(1,822)us-gaap_InterestExpense	(1,976)us-gaap_InterestExpense
Interest income	19us-gaap_InvestmentIncomeInterest	419us-gaap_InvestmentIncomeInterest	30us-gaap_InvestmentIncomeInterest
Other income, net	828us-gaap_OtherNonoperatingIncomeExpense	2,260us-gaap_OtherNonoperatingIncomeExpense	2,175us-gaap_OtherNonoperatingIncomeExpense
Income before income taxes	399,386	276,270	442,619
Income tax provision	154,193us-gaap_IncomeTaxExpenseBenefit	109,375us-gaap_IncomeTaxExpenseBenefit	168,183us-gaap_IncomeTaxExpenseBenefit
Net income	$ 245,193us-gaap_NetIncomeLoss	$ 166,895us-gaap_NetIncomeLoss	$ 274,436us-gaap_NetIncomeLoss
EARNINGS PER SHARE
Basic (in dollars per share)	$ 1.14us-gaap_EarningsPerShareBasic	$ 0.77us-gaap_EarningsPerShareBasic	$ 1.28us-gaap_EarningsPerShareBasic
Diluted (in dollars per share)	$ 1.14us-gaap_EarningsPerShareDiluted	$ 0.77us-gaap_EarningsPerShareDiluted	$ 1.27us-gaap_EarningsPerShareDiluted
Dividends paid per share (in dollars per share)	$ 0.42	$ 0.40	$ 0.52

Aggregate dividends paid during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770