RATES AND REGULATORY ACTIONS (Details) $ in Thousands					1 Months Ended																						12 Months Ended				324 Months Ended
	Nov. 01, 2017 USD ($)	Jul. 01, 2017 USD ($)	Oct. 01, 2016 USD ($)	Feb. 29, 2016 USD ($)	Jan. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	May 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Nov. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jul. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Apr. 30, 2017 USD ($)	Oct. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016 USD ($)	Feb. 29, 2016 USD ($)	Aug. 31, 2014 USD ($)	Feb. 28, 2013 USD ($)	Jul. 31, 2009 USD ($)	Dec. 31, 2018 USD ($) site customer	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2018 USD ($) site customer	Jan. 31, 2017 USD ($)	Jan. 31, 2016 USD ($)	Jun. 30, 2015 USD ($)
Schedule of Capitalization [Line Items]
Public Utilities, Under-Recovered Deferred Balance										$ 53,700
Public Utilities, Funding Level										344,700
Unamortized Remediation Costs																											$ 10,900				$ 10,900
Amount of AIRP																									$ 141,200
Term of AIRP																									4 years
Annual investment amount of AIRP																									$ 35,300
Investment amount of SHARP													$ 110,300											$ 103,500
Investment Approved To Be Recovered Through SHARP											$ 100,300
Investment Requested to be Recovered through SHARP, Term													3 years											3 years
Regulatory assets																												$ 469,224
Amount of statewide funding approved																$ 344,700													$ 344,700
Regulatory costs entity is expensing																12,700													12,700
Number of customers purchasing energy commodity from another entity | customer																											29,141				29,141
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																												2,094
Environmental Remediation Costs: Expended - Net
Schedule of Capitalization [Line Items]
Regulatory assets																												100,327
Weather
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates								$ (800)
Public Utilities, Annual Revenue								6,300
New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)																		$ (11,000)
Requested increase (decrease) in rates								(1,300)
Public Utilities, Annual Revenue								2,200
Roll of AIRP investments into base rates																												80,200
Approved budget																			$ 56,000
South Jersey Gas Company
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)							$ 25,900
Number of sites for environmental cleanup (in sites) | site																											12				12
Regulatory assets																											$ 492,365				$ 492,365
South Jersey Gas Company | Energy Efficiency Tracker
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)																		1,600
Regulatory assets																											2,319				2,319
South Jersey Gas Company | Environmental Remediation Costs: Expended - Net
Schedule of Capitalization [Line Items]
Regulatory assets																											$ 136,227				$ 136,227
South Jersey Gas Company | Storm Hardening and Reliability Program | Building
Schedule of Capitalization [Line Items]
Investments during the period																													35,700	$ 33,700
South Jersey Gas Company | New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)	$ (39,500)
Approved rate of return on rate base, percentage	6.80%
Approved return on common equity, percentage	9.60%
Requested increase (decrease) in rates						$ (3,500)						$ (195,400)
Public Utilities Budget						81,300
Authorized replacement investments (up to)																		$ 302,500
Roll of AIRP investments into base rates							60,400
Amount of statewide funding approved							3,700
Approved budget																			5,600
Increase (decrease) in Universal Service Fund recoveries			$ 1,100				900
South Jersey Gas Company | New Jersey Board of Public Utilities | SHARP Investments
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)														$ (3,600)
Public Utilities, Property, Plant and Equipment, Net														33,300
South Jersey Gas Company | New Jersey Board of Public Utilities | Annual BGSS Filing
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)											4,700			4,700
Public utilities, bill credit																	$ 8,000
Requested increase (decrease) in rates																4,700
South Jersey Gas Company | New Jersey Board of Public Utilities | EET Rate Adjustment Petition
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)													$ (2,600)
Requested increase (decrease) in rates																(3,000)
South Jersey Gas Company | New Jersey Board of Public Utilities | Storm Hardening and Reliability Program
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)																			(3,900)
Requested increase (decrease) in rates																	(3,980)					$ (4,300)
South Jersey Gas Company | New Jersey Board of Public Utilities | AIRP II Investments
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)														(5,000)
Public Utilities, Property, Plant and Equipment, Net														46,100			42,000
South Jersey Gas Company | New Jersey Board of Public Utilities | Annual SBC Filing
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates															$ (8,500)
Accelerated Infrastructure Replacement Program
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates																	$ (4,500)						(13,000)
Amount of AIRP																							$ 500,000
Extension period of AIRP, requested and then received				7 years														5 years
Accelerated Infrastructure Replacement Program | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							(6,600)
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					$ 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
Annual BGSS Filing | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)							(65,500)			(65,500)
Conservation Incentive Program
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates																(200)					(46,500)
Conservation Incentive Program | Non-weather
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates																(1,100)					(9,900)
Conservation Incentive Program | Weather
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates																900					(36,600)
Annual CIP Filing | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							26,400
Allowance for Funds Used Under Construction
Schedule of Capitalization [Line Items]
Approved base rate increase																		$ 5,700
Energy Efficiency Tracker
Schedule of Capitalization [Line Items]
Amount of regulatory costs available for recovery																										$ 17,000						$ 36,300
Contract term																										2 years
Energy Efficiency Tracker | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates										1,600
Societal Benefits Clause
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates																				$ (16,000)
Societal Benefits Clause | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates									$ 3,400
Remediation Adjustment Clause
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates								(6,900)
Number of sites for environmental cleanup (in sites) | site																											12				12
Amortization period																											7 years
Regulated costs recovered																															$ 137,200
Remediation Adjustment Clause | Environmental Remediation Costs: Expended - Net
Schedule of Capitalization [Line Items]
Regulatory assets																											$ 136,200	$ 100,300			136,200
New Jersey Clean Energy Program
Schedule of Capitalization [Line Items]
Amount of statewide funding approved																344,700													344,700					$ 345,000
Regulatory costs entity is expensing																12,700													12,700					$ 14,600
Universal Service Fund
Schedule of Capitalization [Line Items]
Amount of statewide funding approved														38,300
Amount of statewide costs proposed																16,300					56,000								16,300	56,000
Universal Service Fund | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Amount of increase (decrease) in regulatory costs approved														3,200
Amount of statewide funding approved										10,400
Amount of proposed impact of annual costs										900				$ (2,200)		$ (2,000)					$ 1,100								(2,000)	$ 1,100
OSMC Rate Adjustment
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates								(1,100)
State Gas Utilities
Schedule of Capitalization [Line Items]
Public Utilities Budget							45,500
Over Collected Tax
Schedule of Capitalization [Line Items]
Customer Refundable Fees, Refund Payments										5,200
Over Collected Tax | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Credits due to customers under conditions of approval							13,800
Unprotected Excess Deferred Income Tax | South Jersey Gas Company
Schedule of Capitalization [Line Items]
Credits due to customers under conditions of approval							$ 27,500
Public Utilities, Customer Refund Term							5 years
ETG Utility Operations
Schedule of Capitalization [Line Items]
Approved return on common equity, percentage																9.60%
Requested increase (decrease) in rates								(1,200)								$ (13,300)
Public Utilities, Rate Base																$ 720,000													$ 720,000
Public Utilities, After Tax Rate Of Return																5.80%
Public Utilities, Funding Level										10,600
Public Utilities, Annual Revenue							$ 2,200
Public Utilities Budget																											3,000				3,000
Regulatory assets																											169,921				169,921
ETG Utility Operations | Energy Efficiency Tracker
Schedule of Capitalization [Line Items]
Regulatory assets																											0				0
ETG Utility Operations | Environmental Remediation Costs: Expended - Net
Schedule of Capitalization [Line Items]
Regulatory assets																											10,875				10,875
ETG Utility Operations | Annual BGSS Filing
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates											$ (7,100)
ETG Utility Operations | New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Approved requested rate increase (decrease)		$ (12,100)										$ (10,900)
Investment Requested To Be Recovered Through Rider Recovery Mechanism, Amount of IIP						$ 518,000
ETG Utility Operations | CEP Rate Adjustment
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates								1,600
Public Utilities, Annual Revenue								$ 10,000
ETG Utility Operations | USF Filing
Schedule of Capitalization [Line Items]
Public Utilities, Annual Revenue										800
Amount of statewide funding approved										$ 7,200
ETG Utility Operations | State Gas Utilities
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates							(800)
Public Utilities Budget							4,800
ETG Utility Operations
Schedule of Capitalization [Line Items]
Credits due to customers under conditions of approval																											15,000				15,000
Business Combination, Customer Bill Credit Applied							15,000
ELK Utility Operations
Schedule of Capitalization [Line Items]
Credits due to customers under conditions of approval																											$ 300				$ 300
Business Combination, Customer Bill Credit Applied							$ 300
Subsequent Event
Schedule of Capitalization [Line Items]
Approved rate of return on rate base, percentage					6.98%
Approved return on common equity, percentage					9.80%
Requested increase (decrease) in rates					$ (90)
Public Utilities Budget					3,000
Subsequent Event | South Jersey Gas Company | New Jersey Board of Public Utilities
Schedule of Capitalization [Line Items]
Requested increase (decrease) in rates					$ 1,600