SEGMENT REPORTING (Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,648,571	$ 1,532,467
Goodwill	470,633	453,105
Permits and other intangibles, net	507,337	506,818
Total assets	3,712,613	3,431,428
Technical Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	521,040	483,425
Goodwill	57,637	49,267
Permits and other intangibles, net	74,646	73,601
Total assets	859,794	800,060
Industrial and Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	211,712	237,660
Goodwill	106,349	105,286
Permits and other intangibles, net	11,490	14,649
Total assets	366,929	368,858
Kleen Performance Products
Segment Reporting Information [Line Items]
Property, plant and equipment, net	260,608	193,855
Goodwill	68,482	49,755
Permits and other intangibles, net	141,039	140,410
Total assets	605,160	492,483
SK Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	328,655	264,539
Goodwill	238,165	216,589
Permits and other intangibles, net	264,864	256,251
Total assets	920,333	805,488
Lodging Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	99,764	105,208
Goodwill	0	32,208
Permits and other intangibles, net	5,951	7,045
Total assets	142,948	181,357
Oil and Gas Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	139,137	156,286
Goodwill	0	0
Permits and other intangibles, net	9,347	14,862
Total assets	229,480	244,210
Corporate Items
Segment Reporting Information [Line Items]
Property, plant and equipment, net	87,655	91,494
Goodwill	0	0
Permits and other intangibles, net	0	0
Total assets	$ 587,969	$ 538,972