SEGMENT REPORTING (Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,594,987	$ 1,532,467
Goodwill	461,491	453,105
Permits and other intangibles, net	492,224	506,818
Total assets	3,692,381	3,431,428
Technical Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	507,996	483,425
Goodwill	48,688	49,267
Permits and other intangibles, net	69,683	73,601
Total assets	823,881	800,060
Industrial and Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	231,334	237,660
Goodwill	106,605	105,286
Permits and other intangibles, net	13,587	14,649
Total assets	375,796	368,858
Kleen Performance Products
Segment Reporting Information [Line Items]
Property, plant and equipment, net	211,082	193,855
Goodwill	51,109	49,755
Permits and other intangibles, net	139,867	140,410
Total assets	520,943	492,483
SK Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	302,260	264,539
Goodwill	220,824	216,589
Permits and other intangibles, net	251,087	256,251
Total assets	852,082	805,488
Lodging Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	104,386	105,208
Goodwill	34,265	32,208
Permits and other intangibles, net	6,495	7,045
Total assets	181,031	181,357
Oil and Gas Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	146,423	156,286
Goodwill	0	0
Permits and other intangibles, net	11,505	14,862
Total assets	235,775	244,210
Corporate Items
Segment Reporting Information [Line Items]
Property, plant and equipment, net	91,506	91,494
Goodwill	0	0
Permits and other intangibles, net	0	0
Total assets	$ 702,873	$ 538,972