CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues	$ 500,106	$ 443,029	$ 1,002,663	$ 824,790
Cost of revenues	281,279	242,991	555,078	444,243
Selling, general and administrative expenses	43,115	35,956	88,042	72,013
Depreciation and amortization	53,950	44,893	105,520	84,430
Loss (gain) on disposition of assets, net	1,904	(78)	3,308	(1,489)
Operating profit	119,858	119,267	250,715	225,593
Interest expense	(650)	(998)	(1,246)	(2,077)
Interest income	4	3	9	7
Other (expense) income, net	(880)	(10)	40	324
Income before income taxes	118,332	118,262	249,518	223,847
Income tax provision	46,072	45,097	96,503	85,158
Net income	$ 72,260	$ 73,165	$ 153,015	$ 138,689
Earnings per share
Basic (in dollars per share)	$ 0.34	$ 0.34	$ 0.71	$ 0.64
Diluted (in dollars per share)	$ 0.33	$ 0.33	$ 0.71	$ 0.63
Dividends per share (in dollars per share)	$ 0.08	$ 0.05	$ 0.16	$ 0.09
Average shares outstanding
Basic (in shares)	214,893	217,822	215,241	217,672
Diluted (in shares)	216,127	220,262	216,780	220,476