SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)					1 Months Ended		3 Months Ended			6 Months Ended
	Jun. 30, 2020 USD ($) project county shares	Feb. 18, 2020 USD ($)	Aug. 31, 2019 USD ($)	Jul. 01, 2018 USD ($)	Jun. 30, 2020 USD ($) project county shares	Dec. 31, 2019 USD ($) project shares	Jun. 30, 2020 USD ($) project county shares	Mar. 31, 2020 project	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) project county shares	Jun. 30, 2019 USD ($) project	Dec. 31, 2020 project
Public Utilities, General Disclosures [Line Items]
Number of projects closed | project								1		1	7
Number of solar energy sites expected to be sold | project	2				2	3	2			2
Impairment charge							$ 0		$ 0	$ 0	$ 0
Shares of treasury stock held (in shares) | shares	248,411				248,411	231,514	248,411			248,411
Payments to purchase asset management agreement				$ 11,300,000
Minimum annual fee for long-term asset management agreement				$ 4,250,000
Current portion of long-term debt	$ 117,909,000				$ 117,909,000	$ 467,909,000	$ 117,909,000			$ 117,909,000
Notes payable	452,800,000				452,800,000	848,700,000	452,800,000			452,800,000
Debt refinanced	600,000,000.0				$ 600,000,000.0		$ 600,000,000.0			600,000,000.0
Solar Energy Projects Acquisition
Public Utilities, General Disclosures [Line Items]
Consideration paid	$ 2,800,000
Assets held for sale
Public Utilities, General Disclosures [Line Items]
Consideration received on sales or projects										$ 7,200,000	24,300,000
SJG
Public Utilities, General Disclosures [Line Items]
Number of counties in which entity operates | county	7				7		7			7
Impairment charge							$ 0		$ 0	$ 0	$ 0
Refunds received from third party supplier					$ 10,000,000.0
Current portion of long-term debt	$ 27,909,000				27,909,000	417,909,000	27,909,000			27,909,000
Notes payable	160,500,000				160,500,000	171,300,000	160,500,000			160,500,000
Debt refinanced	$ 400,000,000.0				400,000,000.0		400,000,000.0			400,000,000.0
SJG | VSIP
Public Utilities, General Disclosures [Line Items]
VSIP total costs							$ 600,000			600,000
South Jersey Resources Group, LLC
Public Utilities, General Disclosures [Line Items]
Refunds received from third party supplier					$ 11,200,000
Refunds received from third party supplier, amount remaining after remittance										3,900,000
South Jersey Resources Group, LLC | Operating Revenues
Public Utilities, General Disclosures [Line Items]
Refunds received from third party supplier, amount remaining after remittance										3,800,000
South Jersey Resources Group, LLC | Other Income
Public Utilities, General Disclosures [Line Items]
Refunds received from third party supplier, amount remaining after remittance										$ 100,000
ETG Utility Operations
Public Utilities, General Disclosures [Line Items]
Number of counties in which entity operates | county	7				7		7			7
Minimum annual fee for long-term asset management agreement										$ 4,250,000
ETG Utility Operations | South Jersey Resources Group, LLC
Public Utilities, General Disclosures [Line Items]
Refunds received from third party supplier, amount remitted					$ 7,100,000
Forecast
Public Utilities, General Disclosures [Line Items]
Number of solar energy sites expected to be sold | project												2
AEP
Public Utilities, General Disclosures [Line Items]
Consideration paid			$ 4,000,000.0
MTF and ACB | Assets held for sale
Public Utilities, General Disclosures [Line Items]
Consideration received on sales or projects		$ 97,000,000.0				$ 100,000,000.0