INCOME TAXES (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Provision for doubtful accounts	$ 10,715	$ 7,417
Closure, post-closure and remedial liabilities	28,380	28,189
Accrued expenses	15,686	15,382
Accrued compensation	7,774	1,903
Net operating loss carryforwards	43,284	46,650
Tax credit carryforwards	16,909	17,504
Uncertain tax positions accrued interest and federal benefit	519	921
Stock-based compensation	3,440	2,268
Other	7,067	3,258
Total deferred tax assets	133,774	123,492
Deferred tax liabilities:
Property, plant and equipment	(164,246)	(144,325)
Permits and other intangible assets	(103,539)	(107,407)
Prepaids	(9,187)	(8,080)
Total deferred tax liabilities	(276,972)	(259,812)
Total net deferred tax liability before valuation allowance	(143,198)	(136,320)
Less valuation allowance	(79,295)	(68,355)
Net deferred tax liabilities	(222,493)	$ (204,675)
State and local operating loss carryforwards	185,100
Federal operating loss carryforwards	49,800
Foreign operating loss carryforwards	103,300
Foreign tax credit carryforwards	$ 16,500