ACQUISITIONS Narrative (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended		12 Months Ended
	Apr. 04, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Acquisitions, net of cash acquired					$ 0	$ 236,091
Sotera
Business Acquisition [Line Items]
Acquisitions, net of cash acquired	$ 236,100						$ 235,856
Escrow holdback received in business acquisition			$ 200
Goodwill, expected to be tax deductible	103,500
Other intangible assets acquired	60,590
Acquisitioin related costs incurred				$ 2,600		4,300
Integration related costs incurred		$ 800		$ 10,200	$ 1,500	$ 10,200
Backlog and Customer Relationships | Sotera
Business Acquisition [Line Items]
Other intangible assets acquired	$ 60,590