SIGNIFICANT ACCOUNTING POLICIES (Remedial Liabilities) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) site	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Regulatory Liabilities [Line Items]
Remedial Liability | $	$ 124,468	$ 128,007	$ 131,992
Period of time in years over which business acquisitions have been acquired	15 years
Superfund sites owned by third parties	35
Superfund sites	129
Minimum
Regulatory Liabilities [Line Items]
Remedial liabilities at acquisition, inflation rate	1.01%
Remedial liabilities at acquisition, risk-free interest rate	1.37%
Maximum
Regulatory Liabilities [Line Items]
Remedial liabilities at acquisition, inflation rate	2.57%
Remedial liabilities at acquisition, risk-free interest rate	5.99%