CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net income	$ 402,299	$ 377,856	$ 411,744
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	400,922	365,761	347,594
Allowance for doubtful accounts	8,129	5,956	7,783
Amortization of deferred financing costs and debt discount	6,321	5,309	6,301
Accretion of environmental liabilities	13,456	13,667	12,943
Changes in environmental liability estimates	4,139	4,828	8,272
Deferred income taxes	18,437	12,685	17,549
Other expense (income), net	1,454	(2,315)	(2,472)
Stock-based compensation	27,981	20,703	26,844
Loss on early extinguishment of debt	371	2,880	422
Gain on sale of business	0	0	(8,864)
Environmental expenditures	(27,522)	(28,960)	(13,946)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(28,822)	2,453	(201,087)
Inventories and supplies	(49,588)	(4,312)	(74,547)
Other current and non-current assets	(57,220)	(22,645)	(17,303)
Accounts payable	12,327	(27,425)	74,460
Other current and long-term liabilities	45,087	8,111	30,521
Net cash from operating activities	777,771	734,552	626,214
Cash flows used in investing activities:
Additions to property, plant and equipment	(432,241)	(422,300)	(345,056)
Proceeds from sale and disposal of fixed assets	9,099	9,650	8,779
Acquisitions, net of cash acquired	(478,011)	(119,596)	(86,278)
Proceeds from sale of business, net of transaction costs	750	750	16,811
Additions to intangible assets including costs to obtain or renew permits	(9,607)	(2,649)	(1,966)
Purchases of available-for-sale securities	(117,861)	(158,264)	(49,845)
Proceeds from sale of available-for-sale securities	124,197	117,359	68,611
Net cash used in investing activities	(903,674)	(575,050)	(388,944)
Cash flows from (used in) financing activities:
Change in uncashed checks	(1,473)	2,759	552
Tax payments related to withholdings on vested restricted stock	(13,759)	(13,838)	(8,801)
Repurchases of common stock	(55,178)	(51,164)	(50,183)
Deferred financing costs paid	(8,954)	(6,736)	(410)
Payments on finance leases	(30,886)	(15,937)	(12,821)
Proceeds from employee stock purchase plan	3,009	0	0
Principal payments on debt	(15,102)	(623,975)	(115,652)
Proceeds from issuance of debt, net of discount	499,375	500,000	0
Borrowing from revolving credit facility	0	114,000	0
Payment on revolving credit facility	0	(114,000)	0
Net cash from (used in) financing activities	377,032	(208,891)	(187,315)
Effect of exchange rate change on cash	(8,635)	1,484	(9,927)
Increase (decrease) in cash and cash equivalents	242,494	(47,905)	40,028
Cash and cash equivalents, beginning of year	444,698	492,603	452,575
Cash and cash equivalents, end of year	687,192	444,698	492,603
Cash payments for interest and income taxes:
Interest paid	153,059	114,560	105,643
Income taxes paid, net of refunds	130,606	132,314	78,526
Non-cash investing activities:
Property, plant and equipment accrued	43,750	52,376	30,950
Remedial liability assumed in acquisition of property, plant and equipment	$ 0	$ 0	$ 8,092