UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities:
Net income	$ 203,112	$ 188,167
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	195,569	174,455
Allowance for doubtful accounts	4,349	1,209
Amortization of deferred financing costs and debt discount	2,937	2,718
Accretion of environmental liabilities	6,521	6,893
Changes in environmental liability estimates	3,963	387
Deferred income taxes	(88)	(356)
Other expense, net	1,308	1,167
Stock-based compensation	14,853	10,518
Loss on early extinguishment of debt	0	2,362
Environmental expenditures	(9,934)	(16,323)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(116,307)	(5,659)
Inventories and supplies	(28,673)	(1,111)
Other current and long-term assets	(28,870)	(22,749)
Accounts payable	(12,418)	(78,139)
Other current and long-term liabilities	(1,728)	(27,966)
Net cash from operating activities	234,594	235,573
Cash flows used in investing activities:
Additions to property, plant and equipment	(273,023)	(204,298)
Proceeds from sale and disposal of fixed assets	4,295	2,944
Acquisitions, net of cash acquired	(477,201)	(120,636)
Proceeds from sale of business	750	0
Additions to intangible assets including costs to obtain or renew permits	(1,868)	(1,114)
Purchases of available-for-sale securities	(55,318)	(74,451)
Proceeds from sale of available-for-sale securities	71,695	50,290
Net cash used in investing activities	(730,670)	(347,265)
Cash flows from (used in) financing activities:
Change in uncashed checks	(1,868)	2,392
Tax payments related to withholdings on vested restricted stock	(4,599)	(4,335)
Repurchases of common stock	(10,215)	(8,001)
Deferred financing costs paid	(8,148)	(6,346)
Payments on finance leases	(11,491)	(7,588)
Principal payments on debt	(7,551)	(618,975)
Proceeds from issuance of debt, net of discount	499,375	500,000
Borrowing from revolving credit facility	0	114,000
Payment on revolving credit facility	0	(114,000)
Net cash from (used in) financing activities	455,503	(142,853)
Effect of exchange rate change on cash	(2,133)	718
Decrease in cash and cash equivalents	(42,706)	(253,827)
Cash and cash equivalents, beginning of period	444,698	492,603
Cash and cash equivalents, end of period	401,992	238,776
Cash payments for interest and income taxes:
Interest paid	74,079	49,257
Income taxes paid, net of refunds	70,307	92,494
Non-cash investing activities:
Property, plant and equipment accrued	28,315	26,427
ROU assets obtained in exchange for operating lease liabilities	49,420	38,474
ROU assets obtained in exchange for finance lease liabilities	$ 45,174	$ 13,992