CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 344,631	$ 452,575
Short-term marketable securities	70,797	81,724
Accounts receivable, net of allowances aggregating $49,817 and $40,140, respectively	1,005,488	792,734
Unbilled accounts receivable	134,173	94,963
Inventories and supplies	275,696	250,692
Prepaid expenses and other current assets	93,320	68,483
Total current assets	1,924,105	1,741,171
Property, plant and equipment, net	1,913,145	1,863,175
Other assets:
Operating lease right-of-use assets	157,048	161,797
Goodwill	1,244,655	1,227,042
Permits and other intangibles, net	637,254	644,912
Other	48,449	15,602
Total other assets	2,087,406	2,049,353
Total assets	5,924,656	5,653,699
Current liabilities:
Current portion of long-term debt	17,535	17,535
Accounts payable	409,218	359,866
Deferred revenue	94,531	83,749
Accrued expenses and other current liabilities	387,047	391,414
Current portion of closure, post-closure and remedial liabilities	34,551	25,136
Current portion of operating lease liabilities	47,176	47,614
Total current liabilities	990,058	925,314
Other liabilities:
Closure and post-closure liabilities, less current portion of $12,379 and $12,015, respectively	90,618	87,088
Remedial liabilities, less current portion of $22,172 and $13,121, respectively	101,484	98,752
Long-term debt, less current portion	2,510,963	2,517,024
Operating lease liabilities, less current portion	112,854	117,991
Deferred tax liabilities	322,108	314,853
Other long-term liabilities	79,621	78,790
Total other liabilities	3,217,648	3,214,498
Commitments and contingent liabilities (See Note 17)
Stockholders’ equity:
Common stock	541	544
Additional paid-in capital	512,662	536,377
Accumulated other comprehensive loss	(162,702)	(196,012)
Accumulated earnings	1,366,449	1,172,978
Total stockholders’ equity	1,716,950	1,513,887
Total liabilities and stockholders’ equity	$ 5,924,656	$ 5,653,699