COMMITMENTS AND CONTINGENCIES (Details)			1 Months Ended		3 Months Ended								12 Months Ended			468 Months Ended
	Jul. 01, 2018 USD ($)	May 08, 2017 USD ($)	Oct. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) decatherm site contract $ / shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) decatherm site contract $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 1996 USD ($)
Commitment and Contingencies [Line Items]
Maximum purchase amount under contract (in dts/d) | decatherm					772,500								772,500
Minimum length of contract term													4 years
Maximum length of contract term													10 years
Litigation expense paid			$ 22,900,000	$ 59,300,000
Charges to cost of sales					$ 273,873,000	$ 190,366,000	$ 165,341,000	$ 402,387,000	$ 393,432,000	$ 233,112,000	$ 145,796,000	$ 283,068,000
Interest Charges													$ 114,477,000	$ 90,296,000	$ 54,019,000
Accrual for pending litigation					$ 3,100,000				3,200,000				$ 3,100,000	3,200,000		$ 3,200,000
Percentage of workforce that is unionized					45.00%								45.00%
Guarantor obligations					$ 72,300,000								$ 72,300,000
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning of Year								253,650,000				172,855,000	253,650,000	172,855,000
Accruals													15,126,000	58,706,000		642,600,000
Expenditures													(35,891,000)	(51,176,000)		(409,800,000)
Opening Balance Sheet Adjustment													0	73,265,000
End of Year					$ 232,885,000				253,650,000				$ 232,885,000	253,650,000	172,855,000	253,650,000
Capital Units
Commitment and Contingencies [Line Items]
Corporate Unit, stated value per share (in USD per share) | $ / shares					$ 50						$ 50		$ 50
Cost of Sales - Nonutility
Commitment and Contingencies [Line Items]
Charges to cost of sales													$ 351,284,000	258,781,000	199,660,000
Minimum
Accrual for Environmental Loss Contingencies [Roll Forward]
Environmental remediation costs to clean up SJG's sights													101,100,000
Maximum
Accrual for Environmental Loss Contingencies [Roll Forward]
Environmental remediation costs to clean up SJG's sights													186,700,000
Letters of credit
Commitment and Contingencies [Line Items]
Letter of credit provided					$ 9,500,000								$ 9,500,000
Environmental restoration costs
Accrual for Environmental Loss Contingencies [Roll Forward]
EMI's assumed responsibility for environment liabilities, minimum																	$ 100,000
EMI's assumed responsibility for environment liabilities, maximum																	$ 300,000
Environmental restoration costs | Fuel Oil
Accrual for Environmental Loss Contingencies [Roll Forward]
Number of sites affected by environmental remediation | site					5								5
Environmental restoration costs | Minimum | Fuel Oil
Accrual for Environmental Loss Contingencies [Roll Forward]
Estimates of undiscounted future costs					$ 400,000								$ 400,000
Environmental restoration costs | Maximum | Fuel Oil
Accrual for Environmental Loss Contingencies [Roll Forward]
Estimates of undiscounted future costs					800,000								800,000
Parental guarantee
Commitment and Contingencies [Line Items]
Guaranteed Amount					$ 11,300,000								$ 11,300,000
Contract term													2 years
Pricing dispute, long-term gas supply contract
Commitment and Contingencies [Line Items]
Number of long-term gas supply contracts | contract					2								2
South Jersey Resources Group, LLC
Commitment and Contingencies [Line Items]
Amount of monthly fees paid to supplier													$ 7,700,000
South Jersey Resources Group, LLC | Judicial ruling | Pricing dispute, long-term gas supply contract
Commitment and Contingencies [Line Items]
Amount awarded to plaintiff in litigation settlement		$ 59,300,000
Interest Charges													1,100,000	1,000,000.0	4,000,000.0
South Jersey Resources Group, LLC | Judicial ruling | Pricing dispute, long-term gas supply contract | Cost of Sales - Nonutility
Commitment and Contingencies [Line Items]
Charges to cost of sales													500,000	4,100,000	49,600,000
ETG Utility Operations
Commitment and Contingencies [Line Items]
Amount of monthly fees paid to supplier													5,000,000.0
South Jersey Gas Company
Commitment and Contingencies [Line Items]
Amount of monthly fees paid to supplier													1,600,000
Charges to cost of sales					$ 70,542,000	$ 19,268,000	$ 2,654,000	118,880,000	84,383,000	$ 16,079,000	$ 19,379,000	89,808,000	211,344,000	209,649,000	204,432,000
Interest Charges													31,654,000	28,011,000	24,705,000
Accrual for pending litigation					$ 900,000				900,000				$ 900,000	900,000		900,000
Percentage of workforce that is unionized					70.00%								70.00%
Number of sites for environmental cleanup (in number of sites) | site					12								12
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning of Year								$ 148,071,000				$ 171,696,000	$ 148,071,000	171,696,000
Accruals													17,502,000	21,695,000		516,400,000
Expenditures													(34,311,000)	(45,320,000)		(385,100,000)
End of Year					$ 131,262,000				$ 148,071,000				131,262,000	$ 148,071,000	$ 171,696,000	$ 148,071,000
South Jersey Gas Company | Variable-rate demand bonds
Commitment and Contingencies [Line Items]
Letter of credit provided					$ 25,100,000								$ 25,100,000
South Jersey Gas Company | Environmental restoration costs | Majority of the environmental remediation
Accrual for Environmental Loss Contingencies [Roll Forward]
Number of sites affected by environmental remediation | site					6								6
South Jersey Gas Company | Environmental restoration costs | Minimum
Accrual for Environmental Loss Contingencies [Roll Forward]
Estimates of undiscounted future costs					$ 131,300,000								$ 131,300,000
South Jersey Gas Company | Environmental restoration costs | Minimum | Majority of the environmental remediation
Accrual for Environmental Loss Contingencies [Roll Forward]
Estimates of undiscounted future costs					122,400,000								122,400,000
South Jersey Gas Company | Environmental restoration costs | Maximum
Accrual for Environmental Loss Contingencies [Roll Forward]
Estimates of undiscounted future costs					231,400,000								231,400,000
South Jersey Gas Company | Environmental restoration costs | Maximum | Majority of the environmental remediation
Accrual for Environmental Loss Contingencies [Roll Forward]
Estimates of undiscounted future costs					$ 223,300,000								223,300,000
South Jersey Gas Company | Judicial ruling | Pricing dispute, long-term gas supply contract
Commitment and Contingencies [Line Items]
Amount awarded to plaintiff in litigation settlement		$ 22,900,000
ETG Utility Operations
Commitment and Contingencies [Line Items]
Minimal annual fee for AMA contract	$ 4,250,000
Regulatory Asset | South Jersey Gas Company | Judicial ruling | Pricing dispute, long-term gas supply contract
Commitment and Contingencies [Line Items]
Amount awarded to plaintiff in litigation settlement													$ 22,900,000
Environmental restoration costs | ETG Utility Operations
Commitment and Contingencies [Line Items]
Number of sites for environmental cleanup (in number of sites) | site					5								5