SEGMENTS OF BUSINESS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Total Operating Revenues	$ 608,518	$ 365,631	$ 1,944,527	$ 1,351,759
Total Operating (Loss) Income	4,183	(8,973)	190,637	199,464
Total Property Additions	221,305	139,284	490,420	383,503
Total Identifiable Assets	7,917,948		7,917,948		$ 7,308,672
Discontinued Operations
Segment Reporting Information [Line Items]
Total Identifiable Assets	27		27		47
Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues	631,435	380,721	2,011,302	1,400,515
Operating Segments | Corporate and Services
Segment Reporting Information [Line Items]
Total Operating Revenues	15,102	13,577	46,798	39,416
Total Operating (Loss) Income	(4,028)	315	(7,014)	(626)
Total Property Additions	1,242	747	3,562	3,105
Total Identifiable Assets	508,817		508,817		370,899
Operating Segments | Midstream
Segment Reporting Information [Line Items]
Total Property Additions	0	11	0	19
Total Identifiable Assets	0		0		8,970
Operating Segments | SJI Utilities | Subtotal SJI Utilities
Segment Reporting Information [Line Items]
Total Operating Revenues	154,875	107,030	837,318	660,670
Total Operating (Loss) Income	(15,003)	3,673	187,310	199,871
Total Property Additions	142,440	123,911	359,296	345,901
Total Identifiable Assets	6,814,290		6,814,290		6,556,362
Operating Segments | SJI Utilities | SJG Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	112,720	69,958	557,585	412,572
Total Operating (Loss) Income	(2,741)	(1,961)	137,787	133,350
Total Property Additions	70,100	64,988	177,099	186,948
Total Identifiable Assets	3,857,493		3,857,493		3,767,897
Operating Segments | SJI Utilities | ETG Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	42,155	37,072	279,733	248,098
Total Operating (Loss) Income	(12,262)	5,634	49,523	66,521
Total Property Additions	72,340	58,923	182,197	158,953
Total Identifiable Assets	2,956,797		2,956,797		2,788,465
Operating Segments | Energy Management | Subtotal Energy Management
Segment Reporting Information [Line Items]
Total Operating Revenues	454,049	252,762	1,108,865	682,449
Total Operating (Loss) Income	22,231	(14,685)	9,104	(4,630)
Total Property Additions	23	4	(11)	6
Total Identifiable Assets	423,971		423,971		304,736
Operating Segments | Energy Management | Wholesale Energy Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	452,130	247,402	1,103,106	669,067
Total Operating (Loss) Income	21,551	(15,534)	7,326	(5,393)
Total Property Additions	23	4	(11)	6
Total Identifiable Assets	400,963		400,963		278,995
Operating Segments | Energy Management | Retail Services
Segment Reporting Information [Line Items]
Total Operating Revenues	1,919	5,360	5,759	13,382
Total Operating (Loss) Income	680	849	1,778	763
Total Property Additions	0	0	0	0
Total Identifiable Assets	23,008		23,008		25,741
Operating Segments | Energy Production | Subtotal Energy Production
Segment Reporting Information [Line Items]
Total Operating Revenues	7,409	7,352	18,321	17,980
Total Operating (Loss) Income	983	1,724	1,237	4,849
Total Property Additions	77,600	14,611	127,573	34,472
Total Identifiable Assets	529,711		529,711		334,578
Operating Segments | Energy Production | Renewables
Segment Reporting Information [Line Items]
Total Operating Revenues	7,409	7,352	18,321	17,980
Total Operating (Loss) Income	1,240	1,787	2,252	4,920
Total Property Additions	23,317	6,471	34,174	24,458
Total Identifiable Assets	222,895		222,895		195,791
Operating Segments | Energy Production | Decarbonization
Segment Reporting Information [Line Items]
Total Operating Revenues	0	0	0	0
Total Operating (Loss) Income	(257)	(63)	(1,015)	(71)
Total Property Additions	54,283	8,140	93,399	10,014
Total Identifiable Assets	306,816		306,816		138,787
Intersegment Sales
Segment Reporting Information [Line Items]
Total Operating Revenues	(22,917)	$ (15,090)	(66,775)	$ (48,756)
Total Identifiable Assets	$ (358,868)		$ (358,868)		$ (266,920)