CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net (loss) income	$ (39,873)	$ 44,102	$ (28,328)
Adjustments to reconcile net (loss) income to net cash from operating activities:
Depreciation and amortization	287,002	274,194	276,083
Goodwill impairment charges	34,013	31,992	123,414
Allowance for doubtful accounts	6,907	4,793	8,917
Amortization of deferred financing costs and debt discount	3,537	3,280	3,289
Accretion of environmental liabilities	10,177	10,402	10,612
Changes in environmental liability estimates	(4,254)	(11,345)	(3,367)
Deferred income taxes	15,184	1,930	32,320
Other (income) expense, net	(5,685)	1,380	(4,380)
Stock-based compensation	10,481	8,550	8,800
Excess tax benefit of stock-based compensation	(1,198)	(71)	(878)
Net tax benefit (deficiency) on stock-based awards	1,165	(82)	816
Gain on sale of business	(16,884)	0	0
Environmental expenditures	(12,170)	(20,130)	(20,245)
Changes in assets and liabilities:
Accounts receivable and unbilled accounts receivables	(15,009)	55,271	(14,342)
Inventories and supplies	(16,080)	14,059	(21,339)
Other current assets	(8,036)	48,760	(19,030)
Accounts payable	(3,503)	(16,299)	(52,026)
Other current and long-term liabilities	13,850	(54,403)	(2,950)
Net cash from operating activities	259,624	396,383	297,366
Cash flows used in investing activities:
Additions to property, plant and equipment	(219,384)	(257,196)	(257,613)
Proceeds from sales of fixed assets	20,817	6,195	8,164
Acquisitions, net of cash acquired	(206,915)	(94,345)	(16,187)
Additions to intangible assets including costs to obtain or renew permits	(2,831)	(5,296)	(6,519)
Purchase of available-for-sale securities	(598)	0	0
Proceeds on sale of business, net of cash	47,134	0	0
Proceeds from sales of investments	0	0	13,861
Net cash used in investing activities	(361,777)	(350,642)	(258,294)
Cash flows from (used in) financing activities:
Change in uncashed checks	(3,177)	(14,630)	15,069
Proceeds from exercise of stock options	627	397	0
Issuance of restricted shares, net of shares remitted	(2,819)	(2,159)	(2,793)
Repurchases of common stock	(22,188)	(73,347)	(104,341)
Excess tax benefit of stock-based compensation	1,198	71	878
Deferred financing costs paid	(4,031)	0	0
Repayment of long-term obligations	0	0	(5,000)
Proceeds from employee stock purchase plan	0	0	4,364
Payments on capital leases	0	(511)	(2,122)
Issuance of senior unsecured notes, including premium	250,625	0	0
Net cash from (used in) financing activities	220,235	(90,179)	(93,945)
Effect of exchange rate change on cash	4,207	(17,733)	(8,321)
Increase (decrease) in cash and cash equivalents	122,289	(62,171)	(63,194)
Cash and cash equivalents, beginning of year	184,708	246,879	310,073
Cash and cash equivalents, end of year	306,997	184,708	246,879
Cash payments for interest and income taxes:
Interest paid	88,669	73,926	75,408
Income taxes paid	29,255	52,970	42,022
Non-cash investing and financing activities:
Property, plant and equipment accrued	9,214	32,677	23,563
Transfer of inventory to property, plant and equipment	0	0	1,324
Accrued business combination adjustments	0	0	355
Receivable for estimated purchase price adjustment	$ 1,910	$ 1,000	$ 0