SEGMENT REPORTING (Third Party Revenues to Direct Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 755,846	$ 729,520	$ 2,197,575	$ 2,063,113
Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Direct revenues
Segment Reporting Information [Line Items]
Total revenues	755,846	729,520	2,197,575	2,063,113
Technical Services
Segment Reporting Information [Line Items]
Total revenues	246,329	232,482	731,034	680,717
Technical Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	41,366	38,795	121,411	109,217
Technical Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	637	492	1,767	1,547
Technical Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	288,332	271,769	854,212	791,481
Industrial and Field Services
Segment Reporting Information [Line Items]
Total revenues	163,808	172,191	465,264	467,019
Industrial and Field Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(10,262)	(10,867)	(27,688)	(25,464)
Industrial and Field Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	45	(32)	16	(348)
Industrial and Field Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	153,591	161,292	437,592	441,207
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues	315,028	297,082	910,885	821,758
Safety-Kleen | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(31,757)	(28,716)	(95,465)	(86,329)
Safety-Kleen | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	3	1	4	368
Safety-Kleen | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	283,274	268,367	815,424	735,797
Oil, Gas and Lodging Services
Segment Reporting Information [Line Items]
Total revenues	30,026	27,644	89,403	91,555
Oil, Gas and Lodging Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	653	788	1,742	2,576
Oil, Gas and Lodging Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	79	105	218	288
Oil, Gas and Lodging Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	30,758	28,537	91,363	94,419
Corporate Items
Segment Reporting Information [Line Items]
Total revenues	655	121	989	2,064
Corporate Items | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Corporate Items | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	(764)	(566)	(2,005)	(1,855)
Corporate Items | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	$ (109)	$ (445)	$ (1,016)	$ 209