SEGMENT REPORTING (Segment Information, Revenues, EBITA, and Reconciliation to the Consolidated Statement of Operations) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) operation segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Reporting segments number | segment									6
Number of operations for which the revenues are insignificant | operation									2
Total revenues	$ 747,403	$ 755,846	$ 752,788	$ 688,941	$ 692,113	$ 729,520	$ 697,510	$ 636,083	$ 2,944,978	$ 2,755,226	$ 3,275,137
Adjusted EBITDA									425,657	400,354	504,167
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities									9,460	10,177	10,402
Depreciation and amortization									288,422	287,002	274,194
Goodwill impairment charges						34,000			0	34,013	31,992
Income (loss) from operations	27,935	47,663	46,744	5,433	21,943	16,802	34,504	(4,087)	127,775	69,162	187,579
Other expense (income), net	$ 3,305	432	833	$ 1,549	$ (6,932)	198	$ 189	$ 350	6,119	(6,195)	1,380
Loss on early extinguishment of debt		$ 1,900	6,000						7,891	0	0
Gain on sale of businesses			$ (31,700)			$ (16,400)			(30,732)	(16,884)	0
Interest expense, net of interest income									85,808	83,525	76,553
Income (loss) before (benefit) provision for income taxes									58,689	8,716	109,646
Technical Services
Segment Reporting Information [Line Items]
Total revenues									1,144,149	1,056,735	1,139,080
Adjusted EBITDA									276,592	271,176	291,737
Reconciliation to Consolidated Statements of Operations:
Goodwill impairment charges										0
Industrial and Field Services
Segment Reporting Information [Line Items]
Total revenues									593,722	582,215	989,953
Adjusted EBITDA									43,010	51,191	161,447
Reconciliation to Consolidated Statements of Operations:
Goodwill impairment charges										0
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues									1,087,886	996,083	941,689
Adjusted EBITDA									249,811	219,546	172,262
Reconciliation to Consolidated Statements of Operations:
Goodwill impairment charges										0
Oil, Gas and Lodging Services
Segment Reporting Information [Line Items]
Total revenues									119,603	119,883	207,139
Adjusted EBITDA									1,708	(3,292)	11,704
Reconciliation to Consolidated Statements of Operations:
Goodwill impairment charges										34,013
Corporate Items
Segment Reporting Information [Line Items]
Total revenues									(382)	310	(2,724)
Adjusted EBITDA									(145,464)	(138,267)	(132,983)
Direct revenues
Segment Reporting Information [Line Items]
Total revenues									2,944,978	2,755,226	3,275,137
Direct revenues | Technical Services
Segment Reporting Information [Line Items]
Total revenues									980,232	906,495	991,410
Direct revenues | Industrial and Field Services
Segment Reporting Information [Line Items]
Total revenues									631,216	618,245	1,023,638
Direct revenues | Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues									1,213,703	1,110,727	1,060,926
Direct revenues | Oil, Gas and Lodging Services
Segment Reporting Information [Line Items]
Total revenues									117,252	116,692	198,705
Direct revenues | Corporate Items
Segment Reporting Information [Line Items]
Total revenues									2,575	3,067	458
Intersegment revenues, net | Technical Services
Segment Reporting Information [Line Items]
Total revenues									161,533	147,866	144,084
Intersegment revenues, net | Industrial and Field Services
Segment Reporting Information [Line Items]
Total revenues									(37,694)	(35,724)	(32,903)
Intersegment revenues, net | Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues									(125,822)	(115,013)	(119,232)
Intersegment revenues, net | Oil, Gas and Lodging Services
Segment Reporting Information [Line Items]
Total revenues									1,983	2,871	8,051
Intersegment revenues, net | Corporate Items
Segment Reporting Information [Line Items]
Total revenues									0	0	0
Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues									0	0	0
Corporate Items, net | Technical Services
Segment Reporting Information [Line Items]
Total revenues									2,384	2,374	3,586
Corporate Items, net | Industrial and Field Services
Segment Reporting Information [Line Items]
Total revenues									200	(306)	(782)
Corporate Items, net | Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues									5	369	(5)
Corporate Items, net | Oil, Gas and Lodging Services
Segment Reporting Information [Line Items]
Total revenues									368	320	383
Corporate Items, net | Corporate Items
Segment Reporting Information [Line Items]
Total revenues									$ (2,957)	$ (2,757)	$ (3,182)