UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 49,205	$ 16,545
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	220,686	216,932
Allowance for doubtful accounts	6,869	5,635
Amortization of deferred financing costs and debt discount	2,841	2,562
Accretion of environmental liabilities	7,328	7,053
Changes in environmental liability estimates	(301)	(312)
Deferred income taxes	61	184
Stock-based compensation	10,726	9,212
Other expense, net	449	2,814
Gain on sale of business	0	(31,645)
Loss on early extinguishment of debt	2,469	7,891
Environmental expenditures	(7,238)	(10,078)
Changes in assets and liabilities, net of acquisitions
Accounts receivable and unbilled accounts receivable	(76,249)	(38,122)
Inventories and supplies	(20,534)	(4,975)
Other current assets	(523)	18,305
Accounts payable	22,041	(7,085)
Other current and long-term liabilities	29,385	26,553
Net cash from operating activities	247,215	221,469
Cash flows used in investing activities:
Additions to property, plant and equipment	(150,722)	(127,736)
Proceeds from sale and disposal of fixed assets	6,111	5,375
Acquisitions, net of cash acquired	(151,023)	(44,432)
Proceeds from sale of business, net of transactional costs	0	46,339
Additions to intangible assets, including costs to obtain or renew permits	(3,500)	(1,348)
Proceeds from sale of available-for-sale securities	20,123	376
Purchases of available-for-sale securities	(20,471)	0
Net cash used in investing activities	(299,482)	(121,426)
Cash flows used in financing activities:
Change in uncashed checks	(3,476)	(8,657)
Proceeds from exercise of stock options	0	46
Tax payments related to withholdings on vested restricted stock	(2,566)	(2,321)
Repurchases of common stock	(33,581)	(24,465)
Deferred financing costs paid	(3,938)	(5,746)
Premiums paid on early extinguishment of debt	(1,219)	(6,028)
Principal payment on debt	(403,884)	(401,000)
Issuance of senior secured notes, net of discount	348,250	399,000
Borrowing from revolving credit facility	50,000	0
Net cash used in financing activities	(50,414)	(49,171)
Effect of exchange rate change on cash	(1,221)	3,789
(Decrease) increase in cash and cash equivalents	(103,902)	54,661
Cash and cash equivalents, beginning of period	319,399	306,997
Cash and cash equivalents, end of period	215,497	361,658
Cash payments for interest and income taxes:
Interest paid	58,312	67,550
Income taxes paid	16,071	14,321
Non-cash investing activities:
Property, plant and equipment accrued	13,834	14,509
Transfer of inventory to property, plant and equipment	$ 0	$ 12,641