CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues	$ 447,235	$ 471,639	$ 882,197	$ 826,535
Cost of revenues (exclusive of items shown separately below)	307,754	324,280	620,331	584,697
Selling, general and administrative expenses	58,254	50,729	113,048	96,213
Accretion of environmental liabilities	2,407	2,602	4,796	5,304
Depreciation and amortization	26,936	22,105	52,396	44,779
Income from operations	51,884	71,923	91,626	95,542
Other income	2,868	2,708	5,767	3,154
Interest expense, net of interest income of $302 and $546 for the quarter and year-to-date ended 2011 and $165 and $267 for the quarter and year-to-date ended 2010, respectively	(10,642)	(7,646)	(17,120)	(14,574)
Income from continuing operations, before provision for income taxes	44,110	66,985	80,273	84,122
Provision for income taxes	14,954	11,468	28,387	18,557
Income from continuing operations	29,156	55,517	51,886	65,565
Income from discontinued operations, net of tax		2,412		2,794
Net income	$ 29,156	$ 57,929	$ 51,886	$ 68,359
Earnings per share:
Basic (in dollars per share)	$ 0.55	$ 1.10	$ 0.98	$ 1.30
Diluted (in dollars per share)	$ 0.55	$ 1.10	$ 0.97	$ 1.29
Weighted average common shares outstanding (in shares)	52,939	52,581	52,869	52,542
Weighted average common shares outstanding plus potentially dilutive common shares (in shares)	53,362	52,849	53,261	52,796