CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 446,366	$ 306,997
Accounts receivable, net of allowances aggregating $26,782 and $29,249, respectively	512,375	496,226
Unbilled accounts receivable	46,576	36,190
Deferred costs	21,054	18,914
Inventories and supplies	172,540	178,428
Prepaid expenses and other current assets	35,823	56,116
Total current assets	1,234,734	1,092,871
Property, plant and equipment, net	1,602,453	1,611,827
Other assets:
Goodwill	472,819	465,154
Permits and other intangibles, net	482,828	498,721
Other	13,448	13,347
Total other assets	969,095	977,222
Total assets	3,806,282	3,681,920
Current liabilities:
Current portion of long-term obligations	107,798	0
Accounts payable	224,218	229,534
Deferred revenue	72,089	64,397
Accrued expenses	191,495	190,721
Current portion of closure, post-closure and remedial liabilities	23,700	20,016
Total current liabilities	619,300	504,668
Other liabilities:
Closure and post-closure liabilities, less current portion of $6,745 and $6,220, respectively	53,048	52,111
Remedial liabilities, less current portion of $16,955 and $13,796, respectively	109,204	114,211
Long-term obligations, less current portion	1,626,505	1,633,272
Deferred taxes, unrecognized tax benefits and other long-term liabilities	297,288	293,417
Total other liabilities	2,086,045	2,093,011
Commitments and contingent liabilities (See Note 15)
Stockholders’ equity:
Authorized 80,000,000; shares issued and outstanding 57,153,687 and 57,297,978 shares, respectively	572	573
Shares held under employee participation plan	0	(469)
Additional paid-in capital	716,712	725,670
Accumulated other comprehensive loss	(193,177)	(214,326)
Accumulated earnings	576,830	572,793
Total stockholders’ equity	1,100,937	1,084,241
Total liabilities and stockholders’ equity	$ 3,806,282	$ 3,681,920