SEGMENTS OF BUSINESS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 01, 2018
Segment Reporting Information [Line Items]
Total Operating Revenues	$ 463,191	$ 261,203	$ 266,934	$ 637,298	$ 589,583	$ 302,480	$ 227,330	$ 521,945	$ 1,628,626	$ 1,641,338	$ 1,243,068
Total Operating Income									201,205	100,745	8,843
Total Depreciation and Amortization									133,385	132,914	123,486
Total Interest Charges									114,477	90,296	54,019
Total Income Taxes	11,683	(10,925)	(4,646)	24,949	12,767	(16,649)	(31,972)	36,415	21,061	561	(24,937)
Total Property Additions									466,294	350,856	269,747
Property, Plant and Equipment												$ 1,202,435
Total Identifiable Assets	6,365,340				5,956,577				6,365,340	5,956,577
Discontinued Operations
Segment Reporting Information [Line Items]
Total Identifiable Assets	1,766				1,777				1,766	1,777
South Jersey Gas Company
Segment Reporting Information [Line Items]
Total Operating Revenues	172,721	62,039	62,268	272,198	180,369	56,371	76,801	234,459	569,226	548,000	517,254
Total Operating Income									147,494	132,688	138,875
Total Income Taxes	12,201	$ (3,747)	$ 671	$ 23,697	6,913	$ (2,818)	$ 482	$ 21,836	32,822	26,413	45,700
Total Identifiable Assets	3,348,555				3,118,236				3,348,555	3,118,236
Midstream
Segment Reporting Information [Line Items]
Total Identifiable Assets	83,517				72,333				83,517	72,333
ETG Utility Operations
Segment Reporting Information [Line Items]
Property, Plant and Equipment					1,077,000					1,077,000
ELK Utility Operations
Segment Reporting Information [Line Items]
Property, Plant and Equipment					12,300					12,300
Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues									1,685,895	1,716,730	1,311,478
Total Interest Charges									127,629	110,417	69,747
Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues									688,286	914,493	643,195
Total Operating Income									(4,546)	78,815	(35,663)
Total Depreciation and Amortization									89	384	448
Total Interest Charges									0	487	3,400
Total Income Taxes									(361)	20,012	(13,784)
Total Property Additions									11	529	903
Total Identifiable Assets	225,927				318,498				225,927	318,498
Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues									50,790	74,331	106,005
Total Operating Income									(2,140)	(86,412)	(83,437)
Total Depreciation and Amortization									4,591	23,123	47,081
Total Income Taxes									(2,681)	(25,863)	(39,258)
Total Property Additions									229	2,686	12,848
Total Identifiable Assets	154,021				195,329				154,021	195,329
Corporate & Services
Segment Reporting Information [Line Items]
Total Operating Revenues									44,511	51,000	45,024
Total Operating Income									(9,485)	(25,962)	(10,932)
Total Depreciation and Amortization									5,275	12,983	4,303
Total Interest Charges									57,716	54,107	23,819
Total Income Taxes									(16,491)	(16,655)	(17,554)
Total Property Additions									1,554	1,826	2,233
Total Identifiable Assets	403,170				387,482				403,170	387,482
Intersegment Sales
Segment Reporting Information [Line Items]
Total Operating Revenues									(57,269)	(75,392)	(68,410)
Total Interest Charges									(13,152)	(20,121)	(15,728)
Total Identifiable Assets	(332,185)				(301,735)				(332,185)	(301,735)
Utility Operations | Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues									902,308	676,906	517,254
Total Operating Income									217,530	134,596	138,875
Total Depreciation and Amortization									123,430	96,424	71,654
Total Interest Charges									59,014	38,493	24,705
Total Income Taxes									40,729	23,257	45,700
Total Property Additions									464,454	345,696	253,545
Total Identifiable Assets	5,829,124				5,282,893				5,829,124	5,282,893
Utility Operations | Operating Segments | South Jersey Gas Company
Segment Reporting Information [Line Items]
Total Operating Revenues									569,226	548,000	517,254
Total Operating Income									147,494	132,688	138,875
Total Depreciation and Amortization									93,910	82,622	71,654
Total Interest Charges									31,654	28,011	24,705
Total Income Taxes									32,822	26,413	45,700
Total Property Additions									264,235	253,617	253,545
Total Identifiable Assets	3,348,555				3,118,236				3,348,555	3,118,236
Utility Operations | Operating Segments | ETG Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues									325,133	125,604	0
Total Operating Income									69,315	2,164	0
Total Depreciation and Amortization									29,051	13,580	0
Total Interest Charges									27,352	10,478	0
Total Income Taxes									7,761	(3,086)	0
Total Property Additions									197,457	90,259	0
Total Identifiable Assets	2,458,846				2,148,175				2,458,846	2,148,175
Utility Operations | Operating Segments | ELK Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues									7,949	3,302	0
Total Operating Income									721	(256)	0
Total Depreciation and Amortization									469	222	0
Total Interest Charges									8	4	0
Total Income Taxes									146	(70)	0
Total Property Additions									2,762	1,820	0
Total Identifiable Assets	21,723				16,482				21,723	16,482
Wholesale Energy Operations | Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues									607,093	636,005	352,613
Total Operating Income									439	87,895	(36,815)
Total Depreciation and Amortization									89	105	125
Total Interest Charges									0	0	3,150
Total Income Taxes									574	22,473	(14,720)
Total Property Additions									7	34	14
Total Identifiable Assets	195,576				266,417				195,576	266,417
Retail Gas and Other Operations | Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues									0	101,543	111,048
Total Operating Income									0	(8,721)	(2,468)
Total Depreciation and Amortization									0	279	323
Total Interest Charges									0	487	250
Total Income Taxes									0	(2,360)	(544)
Total Property Additions									4	495	889
Total Identifiable Assets	0				12,736				0	12,736
Retail Electric Operations | Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues									81,193	176,945	179,534
Total Operating Income									(4,985)	(359)	3,620
Total Income Taxes									(935)	(101)	1,480
Total Identifiable Assets	30,351				39,345				30,351	39,345
On-Site Energy Production | Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues									48,748	72,374	99,517
Total Operating Income									(4,248)	(88,230)	(83,654)
Total Depreciation and Amortization									4,591	23,123	46,928
Total Interest Charges									8,637	15,364	16,838
Total Income Taxes									(3,308)	(26,397)	(39,262)
Total Property Additions									229	2,686	12,588
Total Identifiable Assets	154,021				195,329				154,021	195,329
Appliance Service Operations | Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues									2,042	1,957	6,488
Total Operating Income									2,108	1,818	217
Total Depreciation and Amortization									0	0	153
Total Income Taxes									627	534	4
Total Property Additions									0	0	260
Total Identifiable Assets	$ 0				$ 0				0	0
Operating Segments | Midstream
Segment Reporting Information [Line Items]
Total Operating Income									(154)	(292)	0
Total Interest Charges									2,262	1,966	985
Total Income Taxes									(135)	(190)	(41)
Total Property Additions									$ 46	$ 119	$ 218