CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 55,441	$ 51,886
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	75,494	52,396
Allowance for doubtful accounts	405	402
Amortization of deferred financing costs and debt discount	753	898
Accretion of environmental liabilities	4,921	4,796
Changes in environmental liability estimates	(3,095)	(773)
Deferred income taxes	(510)	819
Stock-based compensation	3,616	2,880
Excess tax benefit of stock-based compensation	(1,122)	(1,617)
Income tax benefit related to stock option exercises	1,121	1,617
Other expense (income)	374	(2,413)
Environmental expenditures	(3,787)	(5,564)
Changes in assets and liabilities, net of acquisitions
Accounts receivable	54,117	18,063
Other current assets	15,657	(5,252)
Accounts payable	(16,904)	(33,024)
Other current and long-term liabilities	(10,707)	(9,485)
Net cash from operating activities	175,774	75,629
Cash flows from investing activities:
Additions to property, plant and equipment	(82,971)	(65,460)
Proceeds from sales of fixed assets	3,886	4,891
Acquisitions, net of cash acquired	(43,039)	(205,922)
Additions to intangible assets, including costs to obtain or renew permits	(953)	(1,066)
Purchase of marketable securities	(10,517)	0
Proceeds from sales of marketable securities	0	388
Other	5,120	0
Net cash used in investing activities	(128,474)	(267,169)
Cash flows from financing activities:
Change in uncashed checks	(9,496)	13,746
Proceeds from exercise of stock options	98	783
Remittance of shares, net	(1,216)	(1,807)
Proceeds from employee stock purchase plan	3,130	1,556
Deferred financing costs paid	(21)	(8,099)
Payments on capital leases	(3,833)	(3,316)
Distribution of cash earned on employee participation plan	(38)	(189)
Excess tax benefit of stock-based compensation	1,122	1,617
Issuance of senior secured notes, including premium	0	261,250
Net cash from financing activities	(10,254)	265,541
Effect of exchange rate change on cash	(1,011)	1,365
Increase in cash and cash equivalents	36,035	75,366
Cash and cash equivalents, beginning of period	260,723	302,210
Cash and cash equivalents, end of period	296,758	377,576
Cash payments for interest and income taxes:
Interest paid	21,812	11,551
Income taxes paid	4,219	26,454
Non-cash investing and financing activities:
Property, plant and equipment accrued	$ 26,885	$ 24,586