COMMITMENTS AND CONTINGENCIES (Narrative) (Details)	1 Months Ended			3 Months Ended	6 Months Ended
	Jul. 31, 2016 item	Mar. 31, 2016 USD ($) mi	May 31, 2007 entity mi	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Asset Retirement Obligation		$ 220,581,000		$ 223,953,000	$ 223,953,000	$ 226,012,000	$ 223,872,000	$ 217,043,000	$ 226,594,000
Number of groundwater extraction wells | item	2
Cooperating Parties Group [Member]
Loss Contingencies [Line Items]
Number of other companies to perform a Remedial Investigation/ Feasibility Study related to the Lower Passaic River Clean-Up lawsuit | entity			70
Number of miles of the River used in the Remedial Investigation/Feasibility Study | mi			17
Number of miles for bank-to-bank dredging remedy | mi		8
Maximum [Member] | EPA [Member]
Loss Contingencies [Line Items]
Estimated implementation costs					1,380,000,000
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Outstanding standby letters of credit				43,538,000	$ 43,538,000
Hewitt Landfill Matter [Member]
Loss Contingencies [Line Items]
Increase in accrual of liability for claims and litigation				$ 14,216,000