BUSINESS COMBINATIONS (2015 Acquisitions Narrative) (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Apr. 11, 2015	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill amount			$ 8,687	$ 45,791
Thermo Fluids Inc.
Business Acquisition [Line Items]
Purchase price	$ 79,300
Revenue from acquisition included in the company's result of operations				$ 38,000	$ 33,800
Privately Owned Domestic Company
Business Acquisition [Line Items]
Payments to acquire businesses		$ 14,700
Goodwill amount		$ 7,400