SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)				1 Months Ended		3 Months Ended	12 Months Ended
	Feb. 18, 2020 USD ($)	Nov. 30, 2018 USD ($)	Jul. 01, 2018 USD ($)	Dec. 31, 2019 USD ($) project county shares	Jul. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) shares	Dec. 31, 2019 USD ($) project county shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Payments to acquire businesses			$ 1,720,000,000
Number of projects closed | project							7
Number of solar energy sites | project				3			3
Gains (loss) on sale of projects							$ 3,133,000	$ 15,379,000	$ 0
Useful life							15 years
Accumulated depreciation				$ 843,998,000		$ 787,243,000	$ 843,998,000	787,243,000
Accumulated depreciation				$ 13,807,000		52,629,000	13,807,000	52,629,000
Interest capitalized							6,000,000.0	2,500,000	2,000,000.0
Impairment charges						6,100,000	$ 10,800,000	105,300,000	87,800,000
Number of unsold solar energy sites | project				2			2
Impairment of nonutility property and equipment and other noncurrent assets							$ 0	0	0
Amount of costs related to interests in proved and unproved properties in Pennsylvania, net of amortization				$ 8,600,000		$ 8,600,000	$ 8,600,000	$ 8,600,000
Treasury stock held (in shares) | shares				231,514		233,482	231,514	233,482
Long-term debt, current				$ 467,909,000		$ 733,909,000	$ 467,909,000	$ 733,909,000
Notes Payable - Banks				848,700,000		270,500,000	848,700,000	270,500,000
Operating lease right-of-use asset										$ 3,100,000
Operating lease liability				1,851,000			1,851,000			3,100,000
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
AROs, beginning balance							80,163,000	59,497,000
Accretion							9,263,000	1,909,000
Additions							175,082,000	297,000
Settlements							(14,437,000)	(3,402,000)
Revisions in Estimated Cash Flows							13,879,000	21,862,000
AROs, ending balance				$ 263,950,000		80,163,000	$ 263,950,000	$ 80,163,000	$ 59,497,000
South Jersey Gas Company
Schedule of Equity Method Investments [Line Items]
Number of counties in which entity operates | county				7			7
Composite annual rate for all depreciable utility property							2.20%	2.30%	2.20%
Accumulated depreciation				$ 558,634,000		523,743,000	$ 558,634,000	$ 523,743,000
Interest capitalized							4,500,000	2,200,000	$ 1,600,000
Impairment charges							0	0	0
Long-term debt, current				417,909,000		18,909,000	417,909,000	18,909,000
Notes Payable - Banks				171,300,000		107,500,000	171,300,000	107,500,000
Operating lease right-of-use asset				300,000			300,000			500,000
Operating lease liability				313,000			313,000			$ 500,000
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
AROs, beginning balance							79,890,000	58,714,000
Accretion							3,741,000	1,880,000
Additions							2,553,000	297,000
Settlements							(3,554,000)	(2,863,000)
Revisions in Estimated Cash Flows							13,879,000	21,862,000
AROs, ending balance				$ 96,509,000		79,890,000	96,509,000	79,890,000	58,714,000
Solar Assets
Schedule of Equity Method Investments [Line Items]
Gains (loss) on sale of projects							3,100,000	$ 17,600,000
Impairment charges							$ 2,400,000		27,400,000
SJE - Retail Gas Assets
Schedule of Equity Method Investments [Line Items]
Gains (loss) on sale of projects		$ (2,200,000)
Maryland Solar Assets
Schedule of Equity Method Investments [Line Items]
Impairment charges									43,900,000
Landfill
Schedule of Equity Method Investments [Line Items]
Impairment charges									$ 16,500,000
ETG Utility Operations
Schedule of Equity Method Investments [Line Items]
Number of counties in which entity operates | county				7			7
Composite annual rate for all depreciable utility property							2.40%	2.30%
Marina Energy LLC
Schedule of Equity Method Investments [Line Items]
Proceeds from SRECs					$ 62,500,000
Marina Energy LLC | Thermal energy generating property and equipment
Schedule of Equity Method Investments [Line Items]
Impairment charges							$ 8,400,000
Operating lease right-of-use asset				$ 68,900,000			68,900,000
Disposal Group, Held-for-sale, Not Discontinued Operations
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects						228,100,000	24,300,000
Disposal Group, Held-for-sale, Not Discontinued Operations | MTF and ACB
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects				100,000,000.0
Disposal Group, Held-for-sale, Not Discontinued Operations | MTF and ACB | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects	$ 97,000,000.0
Disposal Group, Held-for-sale, Not Discontinued Operations | Elkton Gas
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects				$ 15,000,000.0
Disposal Group, Held-for-sale, Not Discontinued Operations | Solar Assets
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects							$ 2,500,000
Disposal Group, Held-for-sale, Not Discontinued Operations | SJE - Retail Gas Assets
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects		$ 15,000,000.0
Renewable Energy Program | Disposal Group, Held-for-sale, Not Discontinued Operations
Schedule of Equity Method Investments [Line Items]
Amount of impairment to solar assets						$ 99,200,000		$ 99,200,000