UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Cash flows from operating activities:
Net income	$ 58,680	$ 69,832
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	111,980	95,065
Allowance for doubtful accounts	2,825	1,728
Amortization of deferred financing costs and debt discount	1,666	1,329
Accretion of environmental liabilities	3,620	3,217
Changes in environmental liability estimates	(9,863)	917
Deferred income taxes	0	(88)
Other expense, net	932	1,141
Stock-based compensation	7,635	6,338
Environmental expenditures	(2,591)	(4,729)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(74,576)	(44,383)
Inventories and supplies	8,670	(13,572)
Other current and long-term assets	(6,983)	(25,918)
Accounts payable	(10,989)	(17,358)
Other current and long-term liabilities	(89,401)	(54,970)
Net cash from operating activities	1,605	18,549
Cash flows used in investing activities:
Additions to property, plant and equipment	(118,695)	(137,913)
Proceeds from sale and disposal of fixed assets	1,343	1,008
Acquisitions, net of cash acquired	0	(475,306)
Proceeds from sale of business	0	750
Additions to intangible assets including costs to obtain or renew permits	(248)	(534)
Purchases of available-for-sale securities	(24,186)	(31,228)
Proceeds from sale of available-for-sale securities	21,456	33,350
Net cash used in investing activities	(120,330)	(609,873)
Cash flows (used in) from financing activities:
Change in uncashed checks	(1,714)	7,778
Tax payments related to withholdings on vested restricted stock	(8,688)	(3,052)
Repurchases of common stock	(55,000)	(5,000)
Deferred financing costs paid	0	(4,641)
Payments on finance leases	(10,081)	(4,665)
Principal payments on debt	(3,776)	(3,776)
Proceeds from issuance of debt, net of discount	0	499,375
Net cash (used in) from financing activities	(79,259)	486,019
Effect of exchange rate change on cash	209	(1,568)
Decrease in cash and cash equivalents	(197,775)	(106,873)
Cash and cash equivalents, beginning of period	687,192	444,698
Cash and cash equivalents, end of period	489,417	337,825
Cash payments for interest and income taxes:
Interest paid	56,671	51,243
Income taxes paid, net of refunds	9,280	8,020
Non-cash investing activities:
Property, plant and equipment accrued	12,462	28,266
ROU assets obtained in exchange for operating lease liabilities	15,638	23,101
ROU assets obtained in exchange for finance lease liabilities	$ 27,181	$ 14,519