SIGNIFICANT ACCOUNTING POLICIES (Remedial Liabilities) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) site	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Regulatory Liabilities [Line Items]
Remedial Liability | $	$ 121,017	$ 124,468	$ 128,007
Period of time over which business acquisitions have been acquired (in years)	16 years
Superfund sites | site	128
Minimum
Regulatory Liabilities [Line Items]
Remedial liabilities at acquisition, inflation rate (as a percent)	1.01%
Remedial liabilities at acquisition, risk-free interest rate (as a percent)	1.37%
Maximum
Regulatory Liabilities [Line Items]
Remedial liabilities at acquisition, inflation rate (as a percent)	2.57%
Remedial liabilities at acquisition, risk-free interest rate (as a percent)	5.99%