INCOME TAXES (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at Statutory Rate									$ 37,791,000	$ 20,633,000	$ 3,877,000
Increase (Decrease) Resulting from:
State Income Taxes									7,896,000	7,813,000	622,000
State Valuation Allowance									7,392,000	0	0
ESOP Dividend									(627,000)	(697,000)	(791,000)
Tax Reform Adjustments									0	0	(588,000)
AFUDC									(1,901,000)	(1,546,000)	(1,835,000)
Amortization of Excess Deferred Taxes									(6,174,000)	(3,475,000)	(893,000)
Investment and Other Tax Credits									(23,439,000)	(953,000)	(93,000)
Other - Net									1,726,000	(714,000)	262,000
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Continuing Operations	$ 8,939,000	$ (19,467,000)	$ (178,000)	$ 33,370,000	$ 11,683,000	$ (10,925,000)	$ (4,646,000)	$ 24,949,000	22,664,000	21,061,000	561,000
Discontinued Operations									(66,000)	(70,000)	(62,000)
Total Income Tax Expense									22,598,000	20,991,000	499,000
Current:
Federal									0	0	(13,790,000)
State									823,000	(482,000)	3,959,000
Total Current									823,000	(482,000)	(9,831,000)
Deferred:
Federal									3,312,000	11,171,000	13,564,000
State									18,529,000	10,372,000	(3,172,000)
Total Deferred									21,841,000	21,543,000	10,392,000
Continuing Operations	8,939,000	(19,467,000)	(178,000)	33,370,000	11,683,000	(10,925,000)	(4,646,000)	24,949,000	22,664,000	21,061,000	561,000
Discontinued Operations									(66,000)	(70,000)	(62,000)
Total Income Tax Expense									22,598,000	20,991,000	499,000
Deferred Tax Assets:
Net Operating Loss Carryforward	141,252,000				122,197,000				141,252,000	122,197,000
Investment and Other Tax Credits	243,827,000				215,033,000				243,827,000	215,033,000
Conservation Incentive Program	0				1,991,000				0	1,991,000
Deferred State Tax	24,338,000				18,514,000				24,338,000	18,514,000
Income Taxes Recoverable Through Rates	92,739,000				103,922,000				92,739,000	103,922,000
Pension & Other Post Retirement Benefits	34,558,000				28,579,000				34,558,000	28,579,000
Deferred Revenues	4,530,000				5,324,000				4,530,000	5,324,000
Deferred Regulatory Costs	0				11,895,000				0	11,895,000
Provision for Uncollectibles	8,763,000				4,749,000				8,763,000	4,749,000
Other	17,691,000				16,705,000				17,691,000	16,705,000
Total Deferred Tax Asset	567,698,000				528,909,000				567,698,000	528,909,000
Valuation Allowance	(7,392,000)				0				(7,392,000)	0
Total Deferred Tax Asset, net of Valuation Allowance	560,306,000				528,909,000				560,306,000	528,909,000
Deferred Tax Liabilities:
Book versus Tax Basis of Property	512,357,000				479,765,000				512,357,000	479,765,000
Deferred Gas Costs - Net	13,737,000				23,728,000				13,737,000	23,728,000
Derivatives / Unrealized Gain	1,215,000				1,098,000				1,215,000	1,098,000
Environmental Remediation	50,262,000				53,511,000				50,262,000	53,511,000
Deferred Regulatory Costs	13,360,000				0				13,360,000	0
Budget Billing - Customer Accounts	5,248,000				5,400,000				5,248,000	5,400,000
Deferred Pension & Other Post Retirement Benefits	33,307,000				31,416,000				33,307,000	31,416,000
Conservation Incentive Program	6,178,000				0				6,178,000	0
Equity In Loss Of Affiliated Companies	16,019,000				1,801,000				16,019,000	1,801,000
Goodwill Amortization	28,013,000				16,304,000				28,013,000	16,304,000
Other	8,977,000				8,052,000				8,977,000	8,052,000
Total Deferred Tax Liability	688,673,000				621,075,000				688,673,000	621,075,000
Deferred Tax Liability - Net	128,367,000				92,166,000				128,367,000	92,166,000
Valuation allowance	7,392,000				0				7,392,000	0
Accrued interest and penalties on unrecognized tax benefits	900,000				800,000				900,000	800,000	800,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance				1,566,000				1,147,000	1,566,000	1,147,000	1,445,000
Increase as a result of tax positions taken in prior years									806,000	419,000	0
Decrease in prior year positions									0	0	(298,000)
Ending balance	2,372,000				1,566,000				2,372,000	1,566,000	1,147,000
Federal
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	449,088,000								449,088,000
Investment Tax Credit Carryforward	233,964,000								233,964,000
Research and development credits	6,200,000								6,200,000
Federal | 2030
Deferred Tax Liabilities:
Investment Tax Credit Carryforward	11,628,000								11,628,000
Federal | 2031
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	0								0
Investment Tax Credit Carryforward	25,664,000								25,664,000
Federal | 2032
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	14,740,000								14,740,000
Investment Tax Credit Carryforward	32,031,000								32,031,000
Federal | 2033
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	57,363,000								57,363,000
Investment Tax Credit Carryforward	45,606,000								45,606,000
Federal | 2034
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	106,899,000								106,899,000
Investment Tax Credit Carryforward	37,699,000								37,699,000
Federal | 2035
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	51,308,000								51,308,000
Investment Tax Credit Carryforward	45,005,000								45,005,000
Federal | 2036
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	72,199,000								72,199,000
Investment Tax Credit Carryforward	11,744,000								11,744,000
Federal | 2037
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	75,606,000								75,606,000
Investment Tax Credit Carryforward	636,000								636,000
Federal | 2038
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	0								0
Investment Tax Credit Carryforward	93,000								93,000
Federal | 2039
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	0								0
Investment Tax Credit Carryforward	0								0
Federal | 2040
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	0								0
Investment Tax Credit Carryforward	23,858,000								23,858,000
Federal | Indefinite
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	70,973,000								70,973,000
State
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	639,778,000								639,778,000
Research and development credits	4,400,000								4,400,000
State | 2031
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	9,653,000								9,653,000
State | 2032
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	3,108,000								3,108,000
State | 2033
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	18,557,000								18,557,000
State | 2034
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	12,779,000								12,779,000
State | 2035
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	22,472,000								22,472,000
State | 2036
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	147,081,000								147,081,000
State | 2037
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	96,697,000								96,697,000
State | 2038
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	127,846,000								127,846,000
State | 2039
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	130,397,000								130,397,000
State | 2040
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	71,188,000								71,188,000
State | Indefinite
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	0								0
South Jersey Gas Company
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at Statutory Rate									30,111,000	25,245,000	22,966,000
Increase (Decrease) Resulting from:
State Income Taxes									8,965,000	9,542,000	5,220,000
ESOP Dividend									(533,000)	(592,000)	(712,000)
AFUDC									(821,000)	(591,000)	(1,126,000)
Amortization of Excess Deferred Taxes									(3,154,000)	0	0
Other - Net									756,000	(782,000)	65,000
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Continuing Operations	12,167,000	(3,293,000)	1,219,000	25,231,000	12,201,000	(3,747,000)	671,000	23,697,000	35,324,000	32,822,000	26,413,000
Current:
Federal									0	0	(12,766,000)
State									0	0	0
Total Current									0	0	(12,766,000)
Deferred:
Federal									23,976,000	20,744,000	32,571,000
State									11,348,000	12,078,000	6,608,000
Total Deferred									35,324,000	32,822,000	39,179,000
Continuing Operations	12,167,000	$ (3,293,000)	$ 1,219,000	25,231,000	12,201,000	$ (3,747,000)	$ 671,000	23,697,000	35,324,000	32,822,000	26,413,000
Deferred Tax Assets:
Conservation Incentive Program	0				1,991,000				0	1,991,000
Net Operating Loss and Tax Credits	35,301,000				55,250,000				35,301,000	55,250,000
Deferred State Tax	22,918,000				20,352,000				22,918,000	20,352,000
Income Taxes Recoverable Through Rates	58,573,000				68,280,000				58,573,000	68,280,000
Pension & Other Post Retirement Benefits	20,857,000				17,461,000				20,857,000	17,461,000
Deferred Revenues	4,739,000				5,525,000				4,739,000	5,525,000
Provision for Uncollectibles	4,887,000				3,939,000				4,887,000	3,939,000
Other	2,813,000				2,486,000				2,813,000	2,486,000
Total Deferred Tax Asset	150,088,000				175,284,000				150,088,000	175,284,000
Deferred Tax Liabilities:
Book versus Tax Basis of Property	435,764,000				418,059,000				435,764,000	418,059,000
Deferred Gas Costs - Net	10,189,000				20,227,000				10,189,000	20,227,000
Environmental Remediation	46,857,000				47,270,000				46,857,000	47,270,000
Deferred Regulatory Costs	15,087,000				9,609,000				15,087,000	9,609,000
Budget Billing - Customer Accounts	5,248,000				5,400,000				5,248,000	5,400,000
Deferred Pension & Other Post Retirement Benefits	21,398,000				20,396,000				21,398,000	20,396,000
Section 461 Prepayments	1,469,000				1,445,000				1,469,000	1,445,000
Conservation Incentive Program	6,178,000				0				6,178,000	0
Other	11,507,000				10,515,000				11,507,000	10,515,000
Total Deferred Tax Liability	553,697,000				532,921,000				553,697,000	532,921,000
Deferred Tax Liability - Net	403,609,000				357,637,000				403,609,000	357,637,000
Income taxes due to or from related party	0				0				0	0
Accrued interest and penalties on unrecognized tax benefits	900,000				800,000				900,000	800,000	800,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance				$ 1,104,000				$ 1,063,000	1,104,000	1,063,000	1,361,000
Increase as a result of tax positions taken in prior years									25,000	41,000	0
Decrease in prior year positions									0	0	(298,000)
Ending balance	1,129,000				1,104,000				1,129,000	1,104,000	$ 1,063,000
South Jersey Gas Company | Federal
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	67,700,000				156,800,000				67,700,000	156,800,000
Research and development credits	3,000,000.0								3,000,000.0
South Jersey Gas Company | State
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	212,800,000				$ 246,000,000.0				212,800,000	$ 246,000,000.0
Research and development credits	$ 2,500,000								$ 2,500,000