UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 11,572	$ 976
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	74,533	75,355
Allowance for doubtful accounts	4,700	(3,425)
Amortization of deferred financing costs and debt discount	891	1,000
Accretion of environmental liabilities	2,561	2,574
Changes in environmental liability estimates	3,470	(774)
Other expense (income), net	2,365	(2,983)
Stock-based compensation	3,291	5,809
Loss on sale of businesses	3,074	0
Environmental expenditures	(3,435)	(3,264)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(24,960)	12,086
Inventories and supplies	(7,024)	(832)
Other current and non-current assets	8,714	(11,738)
Accounts payable	(5,169)	(27,956)
Other current and long-term liabilities	(40,902)	(17,088)
Net cash from operating activities	33,681	29,740
Cash flows used in investing activities:
Additions to property, plant and equipment	(82,767)	(58,947)
Proceeds from sale and disposal of fixed assets	2,150	4,321
Acquisitions, net of cash acquired	0	(14,870)
Proceeds from sale of businesses, net of transactional costs	7,856	0
Additions to intangible assets including costs to obtain or renew permits	(448)	(1,132)
Proceeds from sale of available-for-sale securities	12,180	8,600
Purchases of available-for-sale securities	(32,058)	(12,941)
Net cash used in investing activities	(93,087)	(74,969)
Cash flows from (used in) financing activities:
Change in uncashed checks	(1,775)	(4,769)
Tax payments related to withholdings on vested restricted stock	(2,224)	(2,276)
Repurchases of common stock	(17,341)	(6,324)
Payments on finance lease	(329)	(115)
Principal payments on debt	(1,884)	(1,884)
Borrowing from revolving credit facility	150,000	0
Net cash from (used in) financing activities	126,447	(15,368)
Effect of exchange rate change on cash	(6,827)	1,461
Increase (decrease) in cash and cash equivalents	60,214	(59,136)
Cash and cash equivalents, beginning of period	371,991	226,507
Cash and cash equivalents, end of period	432,205	167,371
Cash payments for interest and income taxes:
Interest paid	30,648	8,712
Income taxes paid	971	967
Non-cash investing activities:
Property, plant and equipment accrued	12,173	13,002
ROU assets obtained in exchange for operating lease liabilities	12,410	(3,896)
ROU assets obtained in exchange for finance lease liabilities	$ (856)	$ 23,027