BUSINESS COMBINATIONS (Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	9 Months Ended	18 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015	Apr. 11, 2015
Business Acquisition [Line Items]
Goodwill	$ 470,633	$ 470,633	$ 453,105
2016 Acquisitions
Business Acquisition [Line Items]
Accounts receivable	16,368	16,368
Measurement period adjustments, accounts receivable	(1,016)
Inventories and supplies	12,788	12,788
Measurement period adjustment, inventories and supplies	(1,071)
Prepaid and other current assets	929	929
Measurement period adjustment, prepaid and other current assets	9
Property, plant and equipment	130,862	130,862
Measurement period adjustments, property, plant and equipment	(1,843)
Permits and other intangibles	27,056	27,056
Measurement period adjustments, permits and other intangibles	3,651
Deferred tax assets	853	853
Measurement period adjustments, deferred tax assets	(2)
Current liabilities	(19,924)	(19,924)
Measurement period adjustments, current liabilities	(438)
Closure and post-closure liabilities	(2,408)	(2,408)
Measurement period adjustments, closure and post-closure liabilities	(699)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(11,412)	(11,412)
Measurement period adjustments, deferred taxes, unrecognized tax benefits and other long-term liabilities	(1,894)
Total identifiable net assets	155,112	155,112
Measurement period adjustments, total identifiable net assets	(3,303)
Goodwill	50,067	50,067
Measurement period adjustments, goodwill	1,393
Total purchase price, net of cash acquired	205,179	205,179
Measurement period adjustments, total purchase price, net of cash acquired	(1,910)
Thermo Fluids Inc.
Business Acquisition [Line Items]
Accounts receivable	7,301	7,301
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	665
Measurement period adjustment, prepaid and other current assets		(1,084)
Property, plant and equipment	27,641	27,641
Measurement period adjustments, property, plant and equipment		(2,827)
Permits and other intangibles	18,100	18,100
Measurement period adjustments, permits and other intangibles		(1,900)
Current liabilities	(5,884)	(5,884)
Measurement period adjustments, current liabilities		(25)
Closure and post-closure liabilities	(2,333)	(2,333)
Measurement period adjustments, closure and post-closure liabilities		(657)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(9,174)	(9,174)
Measurement period adjustments, deferred taxes, unrecognized tax benefits and other long-term liabilities		3,907
Total identifiable net assets	38,107	38,107
Measurement period adjustments, total identifiable net assets		(2,394)
Goodwill	41,229	41,229
Measurement period adjustments, goodwill		4,638
Total purchase price, net of cash acquired	79,336	79,336
Measurement period adjustments, total purchase price, net of cash acquired		2,244
At Acquisition Dates | 2016 Acquisitions
Business Acquisition [Line Items]
Accounts receivable	17,384	17,384
Inventories and supplies	13,859	13,859
Prepaid and other current assets	920	920
Property, plant and equipment	132,705	132,705
Permits and other intangibles	23,405	23,405
Deferred tax assets	855	855
Current liabilities	(19,486)	(19,486)
Closure and post-closure liabilities	(1,709)	(1,709)
Deferred taxes, unrecognized tax benefits and other long-term liabilities	(9,518)	(9,518)
Total identifiable net assets	158,415	158,415
Goodwill	48,674	48,674
Total purchase price, net of cash acquired	$ 207,089	$ 207,089
At Acquisition Dates | Thermo Fluids Inc.
Business Acquisition [Line Items]
Accounts receivable				$ 7,109
Inventories and supplies				1,791
Prepaid and other current assets				1,749
Property, plant and equipment				30,468
Permits and other intangibles				20,000
Current liabilities				(5,859)
Closure and post-closure liabilities				(1,676)
Deferred taxes, unrecognized tax benefits and other long-term liabilities				(13,081)
Total identifiable net assets				40,501
Goodwill				36,591
Total purchase price, net of cash acquired				$ 77,092