SEGMENT REPORTING (Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,562,254	$ 1,558,834
Goodwill	452,858	452,669
Permits and other intangible, net	534,621	530,080
Total assets	3,746,637	3,704,278
Technical Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	447,937	412,323
Goodwill	49,733	50,092
Permits and other intangible, net	76,883	74,870
Total assets	794,383	756,169
Industrial and Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	254,035	245,115
Goodwill	107,507	109,214
Permits and other intangible, net	16,227	17,801
Total assets	391,560	392,652
Oil Re-refining and Recycling
Segment Reporting Information [Line Items]
Property, plant and equipment, net	196,347	201,451
Goodwill	50,393	50,883
Permits and other intangible, net	146,014	151,041
Total assets	507,585	538,921
SK Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	264,067	240,078
Goodwill	209,555	173,873
Permits and other intangible, net	266,442	252,897
Total assets	807,773	731,072
Lodging Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	122,926	141,965
Goodwill	35,670	34,863
Permits and other intangible, net	8,994	10,744
Total assets	204,561	231,782
Oil and Gas Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	185,312	215,574
Goodwill	0	33,744
Permits and other intangible, net	20,061	22,727
Total assets	288,406	361,223
Corporate Items
Segment Reporting Information [Line Items]
Property, plant and equipment, net	91,630	102,328
Goodwill	0	0
Permits and other intangible, net	0	0
Total assets	$ 752,369	$ 692,459