INCOME TAXES (Details) - USD ($)	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
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at Statutory Rate*									$ 20,633,000	$ 3,877,000	$ (9,915,000)
Increase (Decrease) Resulting from:
State Income Taxes									7,813,000	622,000	2,778,000
ESOP Dividend									(697,000)	(791,000)	(1,314,000)
Tax Reform Adjustments									0	(588,000)	(13,521,000)
AFUDC									(1,546,000)	(1,835,000)	(3,094,000)
Amortization of Excess Deferred Taxes									(3,475,000)	(893,000)	0
Investment and Other Tax Credits									(953,000)	(93,000)	(666,000)
Other - Net									(714,000)	262,000	795,000
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Continuing Operations	$ 11,683,000	$ (10,925,000)	$ (4,646,000)	$ 24,949,000	$ 12,767,000	$ (16,649,000)	$ (31,972,000)	$ 36,415,000	21,061,000	561,000	(24,937,000)
Discontinued Operations									(70,000)	(62,000)	(173,000)
Total Income Tax Expense (Benefit)									20,991,000	499,000	(25,110,000)
Current:
Federal									0	(13,790,000)	(34,971,000)
State									(482,000)	3,959,000	(48,000)
Total Current									(482,000)	(9,831,000)	(35,019,000)
Deferred:
Federal									11,171,000	13,564,000	5,761,000
State									10,372,000	(3,172,000)	4,321,000
Total Deferred									21,543,000	10,392,000	10,082,000
Continuing Operations	11,683,000	(10,925,000)	(4,646,000)	24,949,000	12,767,000	(16,649,000)	(31,972,000)	36,415,000	21,061,000	561,000	(24,937,000)
Discontinued Operations									(70,000)	(62,000)	(173,000)
Deferred Tax Assets:
Net Operating Loss Carryforward	122,197,000				125,418,000				122,197,000	125,418,000
Investment and Other Tax Credits	215,033,000				214,698,000				215,033,000	214,698,000
Conservation Incentive Program	1,991,000				1,701,000				1,991,000	1,701,000
Deferred State Tax	18,514,000				16,087,000				18,514,000	16,087,000
Income Taxes Recoverable Through Rates	103,922,000				103,434,000				103,922,000	103,434,000
Pension & Other Post Retirement Benefits	28,579,000				16,560,000				28,579,000	16,560,000
Deferred Revenues	5,324,000				5,736,000				5,324,000	5,736,000
Deferred Regulatory Costs	11,895,000				0				11,895,000	0
Provision for Uncollectibles	4,749,000				5,319,000				4,749,000	5,319,000
Other	16,705,000				4,639,000				16,705,000	4,639,000
Total Deferred Tax Asset	528,909,000				493,592,000				528,909,000	493,592,000
Deferred Tax Liabilities:
Book versus Tax Basis of Property	479,765,000				458,772,000				479,765,000	458,772,000
Deferred Gas Costs - Net	23,728,000				25,812,000				23,728,000	25,812,000
Derivatives / Unrealized Gain	1,098,000				4,463,000				1,098,000	4,463,000
Environmental Remediation	53,511,000				20,250,000				53,511,000	20,250,000
Deferred Regulatory Costs	0				14,351,000				0	14,351,000
Budget Billing - Customer Accounts	5,400,000				4,550,000				5,400,000	4,550,000
Deferred Pension & Other Post Retirement Benefits	31,416,000				34,095,000				31,416,000	34,095,000
Equity In Loss Of Affiliated Companies	1,801,000				1,417,000				1,801,000	1,417,000
Other	24,356,000				15,718,000				24,356,000	15,718,000
Total Deferred Tax Liability	621,075,000				579,428,000				621,075,000	579,428,000
Deferred Tax Liability - Net	92,166,000				85,836,000				92,166,000	85,836,000
Research and development credits	4,100,000								4,100,000
Accrued interest and penalties on unrecognized tax benefits	800,000				800,000				800,000	800,000	800,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance (beginning)				1,147,000				1,445,000	1,147,000	1,445,000	1,445,000
Increase as a result of tax positions taken in prior years									419,000	0	0
Decrease in prior year positions									0	(298,000)	0
Balance (ending)	1,566,000				1,147,000				1,566,000	1,147,000	1,445,000
Provisional income tax benefit										14,100,000
Federal
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	401,944,000								401,944,000
Investment Tax Credit Carryforward	210,106,000								210,106,000
Alternative minimum tax credits	600,000								600,000
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	21,777,000								21,777,000
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
Federal | Indefinite
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	16,792,000								16,792,000
State
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	521,831,000								521,831,000
State | 2031
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	15,104,000								15,104,000
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	13,317,000								13,317,000
State | 2036
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	165,032,000								165,032,000
State | 2037
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	79,869,000								79,869,000
State | 2038
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	131,406,000								131,406,000
State | 2039
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	82,659,000								82,659,000
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*									25,245,000	22,966,000	41,390,000
Increase (Decrease) Resulting from:
State Income Taxes									9,542,000	5,220,000	5,955,000
ESOP Dividend									(592,000)	(712,000)	(1,182,000)
AFUDC									(591,000)	(1,126,000)	(1,446,000)
Other - Net									(782,000)	65,000	983,000
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Continuing Operations	12,201,000	(3,747,000)	671,000	23,697,000	6,913,000	(2,818,000)	482,000	21,836,000	32,822,000	26,413,000	45,700,000
Current:
Federal									0	(12,766,000)	(33,012,000)
State									0	0	0
Total Current									0	(12,766,000)	(33,012,000)
Deferred:
Federal									20,744,000	32,571,000	69,550,000
State									12,078,000	6,608,000	9,162,000
Total Deferred									32,822,000	39,179,000	78,712,000
Continuing Operations	12,201,000	$ (3,747,000)	$ 671,000	23,697,000	6,913,000	$ (2,818,000)	$ 482,000	21,836,000	32,822,000	26,413,000	45,700,000
Deferred Tax Assets:
Conservation Incentive Program	1,991,000				1,701,000				1,991,000	1,701,000
Net Operating Loss and Tax Credits	55,250,000				60,986,000				55,250,000	60,986,000
Deferred State Tax	20,352,000				16,754,000				20,352,000	16,754,000
Income Taxes Recoverable Through Rates	68,280,000				67,372,000				68,280,000	67,372,000
Pension & Other Post Retirement Benefits	17,461,000				16,699,000				17,461,000	16,699,000
Deferred Revenues	5,525,000				5,906,000				5,525,000	5,906,000
Provision for Uncollectibles	3,939,000				3,776,000				3,939,000	3,776,000
Other	2,486,000				2,599,000				2,486,000	2,599,000
Total Deferred Tax Asset	175,284,000				175,793,000				175,284,000	175,793,000
Deferred Tax Liabilities:
Book versus Tax Basis of Property	418,059,000				395,371,000				418,059,000	395,371,000
Deferred Gas Costs - Net	20,227,000				23,642,000				20,227,000	23,642,000
Environmental Remediation	47,270,000				40,753,000				47,270,000	40,753,000
Deferred Regulatory Costs	9,609,000				5,061,000				9,609,000	5,061,000
Budget Billing - Customer Accounts	5,400,000				4,550,000				5,400,000	4,550,000
Deferred Pension & Other Post Retirement Benefits	20,396,000				21,870,000				20,396,000	21,870,000
Section 461 Prepayments	1,445,000				1,081,000				1,445,000	1,081,000
Other	10,515,000				9,351,000				10,515,000	9,351,000
Total Deferred Tax Liability	532,921,000				501,679,000				532,921,000	501,679,000
Deferred Tax Liability - Net	357,637,000				325,886,000				357,637,000	325,886,000
Income taxes due to or from related party	0				0				0	0
Research and development credits	2,900,000								2,900,000
Accrued interest and penalties on unrecognized tax benefits	800,000				800,000				800,000	800,000	800,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance (beginning)				$ 1,063,000				$ 1,361,000	1,063,000	1,361,000	1,361,000
Increase as a result of tax positions taken in prior years									41,000	0	0
Decrease in prior year positions									0	(298,000)	0
Balance (ending)	1,104,000				1,063,000				1,104,000	1,063,000	$ 1,361,000
Provisional decrease in net deferred tax liabilities										260,500,000
South Jersey Gas Company | Federal
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	156,800,000				200,000,000.0				156,800,000	200,000,000.0
South Jersey Gas Company | State
Deferred Tax Liabilities:
Net Operating Loss Carryforwards	$ 246,000,000.0				$ 207,900,000				$ 246,000,000.0	$ 207,900,000