CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 352,923	$ 184,708
Accounts receivable, net of allowances aggregating $28,436 and $31,426, respectively	503,749	496,004
Unbilled accounts receivable	29,119	25,940
Deferred costs	21,261	18,758
Inventories and supplies	162,404	149,521
Prepaid expenses and other current assets	49,678	46,265
Total current assets	1,119,134	921,196
Property, plant and equipment, net	1,594,987	1,532,467
Other assets:
Deferred financing costs	1,412	1,847
Goodwill	461,491	453,105
Permits and other intangibles, net	492,224	506,818
Other	23,133	15,995
Total other assets	978,260	977,765
Total assets	3,692,381	3,431,428
Current liabilities:
Accounts payable	222,302	241,183
Deferred revenue	70,263	61,882
Accrued expenses	203,813	193,660
Current portion of closure, post-closure and remedial liabilities	24,043	20,395
Total current liabilities	520,421	517,120
Other liabilities:
Closure and post-closure liabilities, less current portion of $8,043 and $7,229, respectively	51,143	49,020
Remedial liabilities, less current portion of $16,000 and $13,166, respectively	114,291	118,826
Long-term obligations	1,631,881	1,382,543
Deferred taxes, unrecognized tax benefits and other long-term liabilities	258,302	267,637
Total other liabilities	2,055,617	1,818,026
Commitments and contingent liabilities
Stockholders’ equity:
Common Stock, $.01 par value: Authorized 80,000,000; shares issued and outstanding 57,495,095 and 57,593,201 shares, respectively	575	576
Shares held under employee participation plan	(469)	(469)
Additional paid-in capital	730,709	738,401
Accumulated other comprehensive loss	(210,233)	(254,892)
Accumulated earnings	595,761	612,666
Total stockholders’ equity	1,116,343	1,096,282
Total liabilities and stockholders’ equity	$ 3,692,381	$ 3,431,428