CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Revenues	$ 572,022	$ 434,962
Cost of revenues (exclusive of items shown separately below)	400,315	312,577
Selling, general and administrative expenses	70,759	54,794
Accretion of environmental liabilities	2,416	2,389
Depreciation and amortization	36,831	25,460
Income from operations	61,701	39,742
Other (expense) income	(299)	2,899
Interest expense, net of interest income of $186 and $244, respectively	(11,272)	(6,478)
Income from continuing operations, before provision for income taxes	50,130	36,163
Provision for income taxes	18,115	13,433
Net Income	$ 32,015	$ 22,730
Earnings per share:
Basic	$ 0.60	$ 0.43
Diluted	$ 0.60	$ 0.43
Weighted average common shares outstanding	53,227	52,798
Weighted average common shares outstanding plus potentially dilutive common shares	53,488	53,158