COMMITMENTS AND CONTINGENT LIABILITIES - LEGAL PROCEEDINGS (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($) site	Sep. 30, 2015 USD ($)
Site Contingency [Line Items]
Number of MGP sites | site		5
Recovery of expenditures, including carrying costs, rolling period approved by the BPU		7 years
Regulatory assets		$ 423,332	$ 410,155
Minimum [Member]
Site Contingency [Line Items]
Litigation settlement, gross		150,900
Maximum [Member]
Site Contingency [Line Items]
Litigation settlement, gross		242,100
Environmental Remediation Costs Expended, Net of Recoveries [Member]
Site Contingency [Line Items]
Regulatory assets		17,963	18,886
Environmental Remediation Costs Liability for Future Expenditures [Member]
Site Contingency [Line Items]
Regulatory assets		$ 180,400	$ 180,400
SBC [Member] | September 2014 SBC Filing [Member]
Site Contingency [Line Items]
Requested rate, amount	$ 8,500