CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 361,658	$ 306,997
Accounts receivable, net of allowances aggregating $28,537 and $29,249, respectively	531,696	496,226
Unbilled accounts receivable	40,933	36,190
Deferred costs	20,237	18,914
Inventories and supplies	173,097	178,428
Prepaid expenses and other current assets	32,637	56,116
Total current assets	1,160,258	1,092,871
Property, plant and equipment, net	1,611,971	1,611,827
Other assets:
Goodwill	478,728	465,154
Permits and other intangibles, net	477,639	498,721
Other	19,757	13,347
Total other assets	976,124	977,222
Total assets	3,748,353	3,681,920
Current liabilities:
Current portion of long-term obligations	4,000	0
Accounts payable	223,599	229,534
Deferred revenue	69,236	64,397
Accrued expenses	213,189	190,721
Current portion of closure, post-closure and remedial liabilities	19,516	20,016
Total current liabilities	529,540	504,668
Other liabilities:
Closure and post-closure liabilities, less current portion of $4,077 and $6,220, respectively	55,762	52,111
Remedial liabilities, less current portion of $15,439 and $13,796, respectively	110,074	114,211
Long-term obligations, less current portion	1,625,971	1,633,272
Deferred taxes, unrecognized tax benefits and other long-term liabilities	298,659	293,417
Total other liabilities	2,090,466	2,093,011
Commitments and contingent liabilities (See Note 15)
Stockholders’ equity:
Authorized 80,000,000; shares issued and outstanding 56,926,549 and 57,297,978 shares, respectively	569	573
Shares held under employee participation plan	0	(469)
Additional paid-in capital	708,358	725,670
Accumulated other comprehensive loss	(169,468)	(214,326)
Accumulated earnings	588,888	572,793
Total stockholders’ equity	1,128,347	1,084,241
Total liabilities and stockholders’ equity	$ 3,748,353	$ 3,681,920