CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 306,997	$ 184,708
Accounts receivable, net of allowances aggregating $29,249 and $31,426, respectively	496,226	496,004
Unbilled accounts receivable	36,190	25,940
Deferred costs	18,914	18,758
Inventories and supplies	178,428	149,521
Prepaid expenses and other current assets	56,116	46,265
Total current assets	1,092,871	921,196
Property, plant and equipment, net	1,611,827	1,532,467
Other assets:
Goodwill	465,154	453,105
Permits and other intangibles, net	498,721	506,818
Other	13,347	17,842
Total other assets	977,222	977,765
Total assets	3,681,920	3,431,428
Current liabilities:
Accounts payable	229,534	241,183
Deferred revenue	64,397	61,882
Accrued expenses	190,721	193,660
Current portion of closure, post-closure and remedial liabilities	20,016	20,395
Total current liabilities	504,668	517,120
Other liabilities:
Closure and post-closure liabilities, less current portion of $6,220 and $7,229, respectively	52,111	49,020
Remedial liabilities, less current portion of $13,796 and $13,166, respectively	114,211	118,826
Long-term obligations	1,633,272	1,382,543
Deferred taxes, unrecognized tax benefits and other long-term liabilities	293,417	267,637
Total other liabilities	2,093,011	1,818,026
Commitments and contingent liabilities (See Note 17)
Stockholders' equity:
Common stock, $.01 par value: Authorized 80,000,000 shares; issued and outstanding 57,297,978 and 57,593,201 shares, respectively	573	576
Shares held under employee participation plan	(469)	(469)
Additional paid-in capital	725,670	738,401
Accumulated other comprehensive loss	(214,326)	(254,892)
Accumulated earnings	572,793	612,666
Total stockholders' equity	1,084,241	1,096,282
Total liabilities and stockholders' equity	$ 3,681,920	$ 3,431,428