RATES AND REGULATORY ACTIONS (Details) $ in Thousands				1 Months Ended																		12 Months Ended			61 Months Ended	300 Months Ended
	Oct. 01, 2016 USD ($)	Feb. 29, 2016 USD ($)	Oct. 01, 2014	Oct. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016 USD ($)	Feb. 29, 2016 USD ($)	Aug. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Aug. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	May 31, 2014 USD ($)	Sep. 30, 2013 USD ($)	Feb. 28, 2013 USD ($)	Jan. 31, 2009 USD ($)	Dec. 31, 2016 USD ($) site customer	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2016 USD ($) site customer	Jan. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jan. 31, 2014 USD ($)	Jun. 30, 2013 USD ($)
Schedule of Capitalization [Line Items]
Approved base rate increase															$ 20,000
Rate of return on base rate															7.10%
Return on common equity															9.75%
Composite depreciation rate			2.10%																						2.40%
Amount of AIRP																				$ 141,200
Term of AIRP																				4 years
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
Regulatory assets																						$ 410,746				$ 410,746		$ 323,434
Number of customers purchasing energy commodity from another entity | customer																						33,467				33,467
Energy Efficiency Tracker
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							$ (800)
Approved request for revenue increase (decrease)		$ (7,900)							$ (7,900)
Regulatory assets																						$ 219				$ 219		496
Environmental Remediation Costs: Expended - Net
Schedule of Capitalization [Line Items]
Regulatory assets																						71,997				71,997		42,032
Deferred pipeline integrity costs
Schedule of Capitalization [Line Items]
Regulatory assets																						4,000				4,000		2,700
New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)				$ 11,000
Roll of AIRP investments into base rates																						80,200
Approved budget					$ 56,000
South Jersey Gas Company | Energy Efficiency Tracker
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)				(1,600)
South Jersey Gas Company | Storm Hardening and Reliability Program | Building
Schedule of Capitalization [Line Items]
Investments during the period																							$ 33,700
South Jersey Gas Company | New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Authorized replacement investments (up to)				$ 302,500
Approved budget					5,600
Increase (decrease) in Universal Service Fund recoveries	$ 1,100
South Jersey Gas Company | New Jersey Board of Public Utilities | Storm Hardening and Reliability Program
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates								$ 4,300
Approved requested rate increase (decrease)					3,900
Accelerated Infrastructure Replacement Program
Schedule of Capitalization [Line Items]
Approved base rate increase															$ 7,500
Requested increase (decrease) in rates									13,000
Amount of AIRP									$ 500,000
Investments to be rolled to base rate															69,900										$ 69,900
Extension period of AIRP, requested and then received		7 years		5 years
Basic Gas Supply Service
Schedule of Capitalization [Line Items]
Bill credits																															$ 11,200
Percent of increase (decrease) in regulatory costs not yet approved																		9.30%
Amount of increase (decrease) in regulatory costs approved															27,000										27,000				$ (28,400)
Requested increase (decrease) in rates												$ (28,400)						$ 27,000
Basic Gas Supply Service | New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)					$ (47,100)
Basic Gas Supply Service | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Bill credits																						$ 10,000				$ 10,000	$ 20,000
Basic Gas Supply Service | South Jersey Gas Company | New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							(47,100)
Conservation Incentive Program
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							46,500					(11,300)						(21,800)
Conservation Incentive Program | Non-weather
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							9,900					(8,800)						4,200
Conservation Incentive Program | Weather
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							36,600					(2,500)						(26,000)
Allowance for Funds Used Under Construction
Schedule of Capitalization [Line Items]
Approved base rate increase				$ 5,700											3,200
Storm Hardening and Reliability Program
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs approved																													4,000
Requested increase (decrease) in rates													$ 4,000
Energy Efficiency Tracker
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs approved										$ 2,600					2,200										2,200
Requested increase (decrease) in rates												(7,600)		$ 56,000				$ 1,400
Period of program																					2 years
Extension period										2 years
Amount of regulatory costs available for recovery										$ 36,300											$ 17,000
Energy Efficiency Tracker | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Amount of regulatory costs available for recovery																																$ 24,000
Societal Benefits Clause
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates						$ 16,000					$ (5,000)						$ (25,700)
Remediation Adjustment Clause
Schedule of Capitalization [Line Items]
Number of sites for environmental cleanup (in sites) | site																						12				12
Amortization period																						7 years
Regulated costs recovered																										$ 112,700
Remediation Adjustment Clause | Environmental Remediation Costs: Expended - Net
Schedule of Capitalization [Line Items]
Regulatory assets																						$ 72,000				$ 72,000		$ 42,000
New Jersey Clean Energy Program
Schedule of Capitalization [Line Items]
Amount of statewide funding approved							345,000					345,000											345,000	345,000						$ 345,000		345,000
Regulatory costs entity is expensing							14,600					14,600											14,600	14,600						14,500		$ 14,500
Universal Service Fund
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs approved															7,900										7,900				5,200
Amount of statewide funding approved															71,800										71,800				46,400
Amount of statewide costs proposed							56,000					(46,400)											56,000	(46,400)						19,900
Amount of proposed impact of annual costs							$ 1,100					$ (3,400)											$ 1,100	$ (3,400)					$ (3,400)	$ 2,600
Amount of increase (decrease) in annual impact approved															$ 2,600										$ 2,600