RATES AND REGULATORY ACTIONS (Details) $ in Thousands	1 Months Ended													12 Months Ended		15 Months Ended	61 Months Ended	288 Months Ended
	Aug. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Aug. 31, 2014 USD ($)	Jan. 31, 2014 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Feb. 28, 2013 USD ($)	Jan. 31, 2013 USD ($)	Jul. 31, 2012 USD ($)	Sep. 30, 2010 USD ($)	Jan. 31, 2010	Jan. 31, 2009 USD ($)	Oct. 31, 2006	Dec. 31, 2015 USD ($) site customer	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) site customer	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($) site customer	Sep. 30, 2015 USD ($)	Jul. 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)	May. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Oct. 31, 2013 USD ($)	Jul. 31, 2013 USD ($)	May. 31, 2013 USD ($)	Jun. 30, 2012 USD ($)	May. 31, 2012 USD ($)
Schedule of Capitalization [Line Items]
Approved base rate increase		$ 20,000								$ 42,100
Rate of return on base rate		7.10%								8.21%
Return on common equity		9.75%								10.30%
Annual depreciation expense reduction attributable to petition										$ 1,200
Investments to be rolled to base rate																											$ 22,500	$ 95,000
Composite depreciate rate																2.10%	2.40%
Term of AIRP							4 years		5 years
Amount of AIRP							$ 141,200		$ 250,000
Annual investment amount of AIRP							$ 35,300
Investment amount of SHARP			$ 103,500		$ 280,000										$ 36,600
Term of SHARP			3 years		7 years
Number of sites for environmental cleanup (in sites) | site														12		12		12
Regulatory assets														$ 323,434		$ 323,434		$ 323,434					$ 357,160
Number of customers purchasing energy commodity from another entity | customer														35,400		35,400		35,400
Amount of incremental expenses requested for deferral						$ 700
Environmental restoration costs expended net [Member]
Schedule of Capitalization [Line Items]
Regulatory assets														$ 42,032		$ 42,032		$ 42,032					29,540
Deferred pipeline integrity costs [Member]
Schedule of Capitalization [Line Items]
Regulatory assets														$ 2,700		$ 2,700		$ 2,700					3,400
Conservation Incentive Program [Member]
Schedule of Capitalization [Line Items]
Approved base rate increase										16,600
Amount of increase (decrease) in regulatory costs requested for recovery not yet approved															(11,300)											$ (21,800)				$ (17,800)
Amount of increase (decrease) in regulatory costs approved					$ 15,500
Regulatory costs, period													3 years
Extension period											1 year
Conservation Incentive Program [Member] | Non-weather Member]
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs requested for recovery not yet approved															(8,800)											4,200				(2,300)
Conservation Incentive Program [Member] | Weather [Member]
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs requested for recovery not yet approved															(2,500)											(26,000)				(15,500)
Capital Investment Recovery Tracker [Member]
Schedule of Capitalization [Line Items]
Approved base rate increase										6,800
Incremental Revenue [Member]
Schedule of Capitalization [Line Items]
Approved base rate increase										$ 18,700
Accelerated Infrastructure Replacement Program [Member]
Schedule of Capitalization [Line Items]
Approved base rate increase		$ 7,500
Investments to be rolled to base rate		69,900															$ 69,900
Basic Gas Supply Service [Member]
Schedule of Capitalization [Line Items]
Proceeds from (repayments for) regulatory action				$ (11,200)				$ (9,400)
Amount of increase (decrease) in regulatory costs requested for recovery not yet approved															(28,400)											$ 27,000				(600)
Amount of increase (decrease) in regulatory costs approved		27,000			(600)												27,000		$ (28,400)
Percent of increase (decrease) in regulatory costs not yet approved																										9.30%
Storm Hardening and Reliability Program [Member]
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs requested for recovery not yet approved																					$ 4,000
Amount of increase (decrease) in regulatory costs approved																			4,000
Energy Efficiency Tracker [Member]
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs requested for recovery not yet approved															(7,600)							$ 56,000				$ 1,400				$ 2,200	$ 5,800	$ 3,100
Amount of increase (decrease) in regulatory costs approved	$ 2,600	2,200				24,000											2,200												$ 2,100
Regulatory costs, period												2 years
Extension period	2 years
Amount of regulatory costs available for recovery	$ 36,300											$ 17,000
Societal Benefits Clause [Member]
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs requested for recovery not yet approved																				$ (5,000)				$ (25,700)					$ (6,400)
Remediation Adjustment Clause [Member]
Schedule of Capitalization [Line Items]
Number of sites for environmental cleanup (in sites) | site														12		12		12
Amortization period														7 years
Regulated costs recovered																		$ 110,500
Remediation Adjustment Clause [Member] | Environmental restoration costs expended net [Member]
Schedule of Capitalization [Line Items]
Regulatory assets														$ 42,000		$ 42,000		$ 42,000					$ 29,500
New Jersey Clean Energy Program [Member]
Schedule of Capitalization [Line Items]
Amount of statewide funding approved						345,000									345,000										$ 345,000
Regulatory costs entity is expensing						14,500									14,600										14,500
Universal Service Fund [Member]
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs approved		7,900			5,800												7,900		5,200
Amount of statewide funding approved		71,800			54,400												71,800		46,400
Amount of statewide costs proposed						(29,400)									(46,400)										19,900
Amount of proposed impact of annual costs						$ (3,700)									$ (3,400)				$ (3,400)						$ 2,600
Amount of increase (decrease) in annual impact approved		$ 2,600			$ (3,400)												$ 2,600