BUSINESS COMBINATIONS (Assets Aquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Apr. 11, 2015
Business Acquisition [Line Items]
Goodwill	$ 460,642	$ 453,105
Thermo Fluids Inc.
Business Acquisition [Line Items]
Accounts receivable	7,301		$ 7,109
Measurement period adjustments, accounts receivable	192
Inventories and supplies	1,791		1,791
Measurement period adjustment, inventories and supplies	0
Prepaid and other current assets	665		1,749
Measurement period adjustment, prepaid and other current assets	(1,084)
Property, plant and equipment	27,641		30,468
Measurement period adjustments, property, plant and equipment	(2,827)
Permits and other intangibles	18,100		20,000
Measurement period adjustments, permits and other intangibles	(1,900)
Current liabilities	(5,884)		(5,859)
Measurement period adjustments, current liabilities	(25)
Closure and post-closure liabilities	(2,333)		(1,676)
Measurement period adjustments, closure and post-closure liabilities	(657)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(9,174)		(13,081)
Measurement period adjustments, deferred taxes, unrecognized tax benefits and other long-term liabilities	3,907
Total identifiable net assets	38,107		40,501
Measurement period adjustments, total identifiable net assets	(2,394)
Goodwill	41,229		36,591
Measurement period adjustments, goodwill	4,638
Total	79,336		$ 77,092
Measurement period adjustments, total	$ 2,244