CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
REVENUES	$ 1,945,023	$ 1,809,807	$ 1,096,384
COSTS AND EXPENSES:
Cost of revenues	1,105,886	992,704	606,098
Selling, general and administrative expenses	175,749	151,286	121,839
Depreciation and amortization	214,899	179,905	133,360
Loss (gain) on disposition of assets, net	6,099	3,831	(3,758)
Operating profit	442,390	482,081	238,845
Interest expense	(1,976)	(3,453)	(2,662)
Interest income	30	18	46
Other income, net	2,175	169	1,303
Income before income taxes	442,619	478,815	237,532
Income tax provision	168,183	182,434	90,790
Net income	$ 274,436	$ 296,381	$ 146,742
EARNINGS PER SHARE
Basic (in dollars per share)	$ 1.28	$ 1.36	$ 0.67
Diluted (in dollars per share)	$ 1.27	$ 1.35	$ 0.67
Dividends paid per share (in dollars per share)	$ 0.520	$ 0.213	$ 0.094