SEGMENTS OF BUSINESS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Total Operating Revenues	$ 511,431	$ 311,828	$ 1,336,009	$ 986,128
Total Operating (Loss) Income	(12,146)	11,609	186,454	208,437
Total Property Additions	142,044	147,323	269,115	244,219
Total Identifiable Assets	7,660,601		7,660,601		$ 7,308,672
Discontinued Operations
Segment Reporting Information [Line Items]
Total Identifiable Assets	4		4		47
Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues	530,012	324,828	1,379,867	1,019,794
Operating Segments | Corporate and Services
Segment Reporting Information [Line Items]
Total Operating Revenues	15,262	12,046	31,696	25,839
Total Operating (Loss) Income	1,005	(1,119)	(2,986)	(941)
Total Property Additions	802	1,614	2,320	2,358
Total Identifiable Assets	409,333		409,333		370,899
Operating Segments | Midstream
Segment Reporting Information [Line Items]
Total Property Additions	0	4	0	8
Total Identifiable Assets	0		0		8,970
Operating Segments | SJI Utilities | Subtotal SJI Utilities
Segment Reporting Information [Line Items]
Total Operating Revenues	183,944	144,696	682,443	553,640
Total Operating (Loss) Income	17,327	19,336	202,313	196,198
Total Property Additions	114,107	127,451	216,856	221,990
Total Identifiable Assets	6,690,829		6,690,829		6,556,362
Operating Segments | SJI Utilities | SJG Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	122,602	91,215	444,865	342,614
Total Operating (Loss) Income	14,826	16,469	140,528	135,311
Total Property Additions	55,853	68,551	106,999	121,960
Total Identifiable Assets	3,807,073		3,807,073		3,767,897
Operating Segments | SJI Utilities | ETG Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	61,342	53,481	237,578	211,026
Total Operating (Loss) Income	2,501	2,867	61,785	60,887
Total Property Additions	58,254	58,900	109,857	100,030
Total Identifiable Assets	2,883,756		2,883,756		2,788,465
Operating Segments | Energy Management | Subtotal Energy Management
Segment Reporting Information [Line Items]
Total Operating Revenues	325,250	163,881	654,816	429,687
Total Operating (Loss) Income	(31,757)	(7,033)	(13,127)	10,055
Total Property Additions	(34)	2	(34)	2
Total Identifiable Assets	370,103		370,103		304,736
Operating Segments | Energy Management | Wholesale Energy Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	323,479	159,755	650,976	421,665
Total Operating (Loss) Income	(31,676)	(7,167)	(14,225)	10,141
Total Property Additions	(34)	2	(34)	2
Total Identifiable Assets	347,868		347,868		278,995
Operating Segments | Energy Management | Retail Services
Segment Reporting Information [Line Items]
Total Operating Revenues	1,771	4,126	3,840	8,022
Total Operating (Loss) Income	(81)	134	1,098	(86)
Total Property Additions	0	0		0
Total Identifiable Assets	22,235		22,235		25,741
Operating Segments | Energy Production | Subtotal Energy Production
Segment Reporting Information [Line Items]
Total Operating Revenues	5,556	4,205	10,912	10,628
Total Operating (Loss) Income	1,279	425	254	3,125
Total Property Additions	27,169	18,252	49,973	19,861
Total Identifiable Assets	447,000		447,000		334,578
Operating Segments | Energy Production | Renewables
Segment Reporting Information [Line Items]
Total Operating Revenues	5,556	4,205	10,912	10,628
Total Operating (Loss) Income	1,592	433	1,012	3,133
Total Property Additions	5,374	17,214	10,857	17,987
Total Identifiable Assets	195,445		195,445		195,791
Operating Segments | Energy Production | Decarbonization
Segment Reporting Information [Line Items]
Total Operating Revenues	0	0	0	0
Total Operating (Loss) Income	(313)	(8)	(758)	(8)
Total Property Additions	21,795	1,038	39,116	1,874
Total Identifiable Assets	251,555		251,555		138,787
Intersegment Sales
Segment Reporting Information [Line Items]
Total Operating Revenues	(18,581)	$ (13,000)	(43,858)	$ (33,666)
Total Identifiable Assets	$ (256,668)		$ (256,668)		$ (266,920)