SEGMENTS OF BUSINESS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total Operating Revenues	$ 1,991,996	$ 1,541,383	$ 1,628,626
Total Operating Income	349,120	282,222	201,205
Total Depreciation and Amortization	211,652	170,647	133,385
Total Interest Charges	127,130	118,534	114,477
Total Income Taxes	47,107	22,664	21,061
Total Property Additions	566,568	552,925	466,294
Total Identifiable Assets	7,308,672	6,689,148
Discontinued Operations
Segment Reporting Information [Line Items]
Total Identifiable Assets	47	1,775
Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues	2,073,795	1,605,852	1,685,895
Total Interest Charges	133,981	125,836	127,629
Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Interest Charges	6,173	4,001	8,637
Intersegment
Segment Reporting Information [Line Items]
Total Operating Revenues	(81,799)	(64,469)	(57,269)
Total Interest Charges	(6,851)	(7,302)	(13,152)
Total Identifiable Assets	(266,920)	(225,331)
SJG Utility Operations | Operating Segments | SJI Utilities
Segment Reporting Information [Line Items]
Total Operating Revenues	618,426	571,787	569,226
Total Operating Income	199,214	171,235	147,494
Total Depreciation and Amortization	127,440	101,711	93,910
Total Interest Charges	39,133	33,388	31,654
Total Income Taxes	38,414	35,324	32,822
Total Property Additions	243,699	266,009	264,235
Total Identifiable Assets	3,767,897	3,522,265
ETG Utility Operations | Operating Segments | SJI Utilities
Segment Reporting Information [Line Items]
Total Operating Revenues	360,024	349,392	325,133
Total Operating Income	95,509	89,638	69,315
Total Depreciation and Amortization	70,643	57,967	29,051
Total Interest Charges	34,155	29,997	27,352
Total Income Taxes	15,053	12,465	7,761
Total Property Additions	224,019	197,730	197,457
Total Identifiable Assets	2,788,465	2,561,067
ELK Utility Operations | Operating Segments | SJI Utilities
Segment Reporting Information [Line Items]
Total Operating Revenues	0	4,793	7,949
Total Operating Income	0	372	721
Total Depreciation and Amortization	0	354	469
Total Interest Charges	0	21	8
Total Income Taxes	0	186	146
Total Property Additions	0	970	2,762
Subtotal SJI Utilities | Operating Segments | SJI Utilities
Segment Reporting Information [Line Items]
Total Operating Revenues	978,450	925,972	902,308
Total Operating Income	294,723	261,245	217,530
Total Depreciation and Amortization	198,083	160,032	123,430
Total Interest Charges	73,288	63,406	59,014
Total Income Taxes	53,467	47,975	40,729
Total Property Additions	467,718	464,709	464,454
Total Identifiable Assets	6,556,362	6,083,332
Wholesale Energy Operations | Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	993,938	571,590	607,093
Total Operating Income	48,406	33,869	439
Total Depreciation and Amortization	92	69	89
Total Income Taxes	14,035	9,666	574
Total Property Additions	6	6	7
Total Identifiable Assets	278,995	195,882
Retail Services | Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	17,889	38,251	83,845
Total Operating Income	1,838	(3,153)	(2,764)
Total Depreciation and Amortization	537	0	0
Total Interest Charges	180	43	(142)
Total Income Taxes	1,537	287	(262)
Total Property Additions	55	0	4
Total Identifiable Assets	25,741	29,687
Subtotal Energy Management | Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	1,011,827	609,841	690,938
Total Operating Income	50,244	30,716	(2,325)
Total Depreciation and Amortization	629	69	89
Total Interest Charges	180	43	(142)
Total Income Taxes	15,572	9,953	312
Total Property Additions	61	6	11
Total Identifiable Assets	304,736	225,569
Renewables | Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues	24,038	15,617	48,748
Total Operating Income	4,569	(5,602)	(4,248)
Total Depreciation and Amortization	5,106	5,647	4,591
Total Interest Charges	4,660	4,001	8,637
Total Income Taxes	(8,124)	(24,132)	(3,308)
Total Property Additions	64,906	85,280	229
Total Identifiable Assets	195,791	153,018
Decarbonization | Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues	0	0	0
Total Operating Income	(120)	0	0
Total Depreciation and Amortization	0	0	0
Total Interest Charges	1,513	0	0
Total Income Taxes	146	0	0
Total Property Additions	29,600	0	0
Total Identifiable Assets	138,787	40,482
Subtotal Energy Production | Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues	24,038	15,617	48,748
Total Operating Income	4,449	(5,602)	(4,248)
Total Depreciation and Amortization	5,106	5,647	4,591
Total Income Taxes	(7,978)	(24,132)	(3,308)
Total Property Additions	94,506	85,280	229
Total Identifiable Assets	334,578	193,500
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Total Operating Income	0	(467)	(154)
Total Interest Charges	1,704	2,513	2,262
Total Income Taxes	(329)	(217)	(135)
Total Property Additions	29	131	46
Total Identifiable Assets	8,970	92,208
Corporate & Services | Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues	59,480	54,422	43,901
Total Operating Income	(296)	(3,670)	(9,598)
Total Depreciation and Amortization	7,834	4,899	5,275
Total Interest Charges	52,636	55,873	57,858
Total Income Taxes	(13,625)	(10,915)	(16,537)
Total Property Additions	4,254	2,799	$ 1,554
Total Identifiable Assets	$ 370,899	$ 318,095