SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)		1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 01, 2018 USD ($)	Nov. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) county mi shares	Dec. 31, 2018 USD ($) county mi shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)	Jul. 31, 2018 USD ($)	Jun. 27, 2018 MW
Schedule of Equity Method Investments [Line Items]
Length of natural gas pipeline (in miles) | mi			118	118
Payments to acquire businesses	$ 1,740,000,000
Composite annual rate for all depreciable utility property				2.30%	2.20%	2.20%
Useful life				50 years
Accumulated depreciation			$ 787,243,000	$ 787,243,000	$ 498,161,000
Accumulated depreciation			52,629,000	52,629,000	194,913,000
Interest capitalized				2,500,000	2,000,000	$ 6,600,000
Impairment charges			6,100,000	105,300,000	87,800,000	0
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	$ 8,700,000
Treasury stock held (in shares) | shares			233,482	233,482	216,642
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
AROs as of January 1,				$ 59,497,000	$ 59,427,000
Accretion				1,909,000	1,955,000
Additions				297,000	1,008,000
Settlements				(3,402,000)	(2,893,000)
Revisions in Estimated Cash Flows				21,862,000	0
ARO's as of December 31,			$ 80,163,000	80,163,000	59,497,000	59,427,000
Increase in contract retirement costs				31,500,000
Change in discount and inflation rates				9,600,000
Gain (Loss) on Disposition of Assets				$ 15,379,000	0	0
South Jersey Gas Company
Schedule of Equity Method Investments [Line Items]
Number of counties in which entity operates | county			7	7
Accumulated depreciation			$ 523,743,000	$ 523,743,000	498,161,000
Interest capitalized				2,200,000	1,600,000	5,300,000
Impairment charges				0	0	0
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
AROs as of January 1,				58,714,000	58,674,000
Accretion				1,880,000	1,925,000
Additions				297,000	1,008,000
Settlements				(2,863,000)	(2,893,000)
Revisions in Estimated Cash Flows				21,862,000	0
ARO's as of December 31,			$ 79,890,000	$ 79,890,000	58,714,000	$ 58,674,000
Maryland Solar Assets
Schedule of Equity Method Investments [Line Items]
Impairment charges					43,900,000
Solar Assets
Schedule of Equity Method Investments [Line Items]
Impairment charges					27,400,000
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
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Gain (Loss) on Disposition of Assets				$ 17,600,000
Disposal Group, Held-for-sale, Not Discontinued Operations
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects			$ 228,100,000
Fair value of assets held for sale			59,600,000	59,600,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Solar Assets
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects				4,800,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Retail Gas Assets
Schedule of Equity Method Investments [Line Items]
Consideration received on sales or projects		$ 15,000,000
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Gain (Loss) on Disposition of Assets		(2,200,000)
Disposal Group, Held-for-sale, Not Discontinued Operations | Marina Energy LLC
Schedule of Equity Method Investments [Line Items]
Capacity of solar energy projects | MW								204
Equity interests								100.00%
Cash payment for sale							$ 62,500,000
SJE - Retail Gas Assets | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Schedule of Equity Method Investments [Line Items]
Total consideration		$ 15,000,000
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