INCOME TAXES (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at Statutory Rate									$ 3,877,000	$ (9,915,000)	$ 60,624,000
Increase (Decrease) Resulting from:
State Income Taxes									622,000	2,778,000	6,438,000
ESOP Dividend									(791,000)	(1,314,000)	(1,300,000)
Tax Reform Adjustments									(588,000)	(13,521,000)	0
AFUDC									(1,835,000)	(3,094,000)	(900,000)
Amortization of Excess Deferred Taxes									(893,000)	0	0
Investment and Other Tax Credits									(93,000)	(666,000)	(10,706,000)
Other - Net									262,000	795,000	(5,000)
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Continuing Operations	$ 12,767,000	$ (16,649,000)	$ (31,972,000)	$ 36,415,000	$ (16,498,000)	$ (24,765,000)	$ (5,544,000)	$ 21,870,000	561,000	(24,937,000)	54,151,000
Discontinued Operations									(62,000)	(173,000)	(133,000)
Total Income Tax (Benefit) Expense									499,000	(25,110,000)	54,018,000
Current:
Federal									(13,790,000)	(34,971,000)	0
State									3,959,000	(48,000)	(1,638,000)
Total Current									(9,831,000)	(35,019,000)	(1,638,000)
Deferred:
Federal									13,564,000	5,761,000	44,246,000
State									(3,172,000)	4,321,000	11,543,000
Total Deferred									10,392,000	10,082,000	55,789,000
Continuing Operations	12,767,000	(16,649,000)	(31,972,000)	36,415,000	(16,498,000)	(24,765,000)	(5,544,000)	21,870,000	561,000	(24,937,000)	54,151,000
Discontinued Operations									(62,000)	(173,000)	(133,000)
Deferred Tax Assets:
Net Operating Loss Carryforward												$ 125,418,000	$ 152,541,000
Investment and Other Tax Credits												214,698,000	214,605,000
Derivatives / Unrealized Loss												0	2,068,000
Conservation Incentive Program												1,701,000	0
Deferred State Tax												16,087,000	16,905,000
Income Taxes Recoverable Through Rates												103,434,000	76,426,000
Pension & Other Post Retirement Benefits												16,560,000	16,624,000
Deferred Revenues												5,736,000	5,726,000
Provision for Uncollectibles												5,319,000	3,854,000
Other												4,639,000	1,949,000
Total Deferred Tax Asset												493,592,000	490,698,000
Deferred Tax Liabilities:
Book versus Tax Basis of Property												458,772,000	486,854,000
Deferred Gas Costs - Net												25,812,000	10,254,000
Derivatives / Unrealized Gain												4,463,000	0
Environmental Remediation												20,250,000	31,393,000
Deferred Regulatory Costs												14,351,000	3,554,000
Budget Billing - Customer Accounts												4,550,000	4,043,000
Deferred Pension & Other Post Retirement Benefits												34,095,000	21,349,000
Conservation Incentive Program												0	7,721,000
Equity In Loss Of Affiliated Companies												1,417,000	1,377,000
Other												15,718,000	11,037,000
Total Deferred Tax Liability												579,428,000	577,582,000
Deferred Tax Liability - Net												85,836,000	86,884,000
Research and development credits												3,200,000
Unrecognized tax benefits	1,147,000			1,445,000	1,445,000			1,445,000	1,445,000	1,445,000	559,000	1,147,000	1,445,000	$ 1,445,000
Accrued interest and penalties on unrecognized tax benefits												800,000	800,000	700,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance (beginning)				1,445,000				1,445,000	1,445,000	1,445,000	559,000
Increase as a result of tax positions taken in prior years									0	0	886,000
Decrease in prior year positions									(298,000)	0	0
Balance (ending)	1,147,000				1,445,000				1,147,000	1,445,000	1,445,000
Provisional income tax benefit									14,100,000
Federal
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												442,489,000
Investment Tax Credit Carryforward												210,106,000
Alternative minimum tax credits												1,200,000
Federal | 2030
Deferred Tax Liabilities:
Investment Tax Credit Carryforward												11,628,000
Federal | 2031
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												36,126,000
Investment Tax Credit Carryforward												25,664,000
Federal | 2032
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												42,988,000
Investment Tax Credit Carryforward												32,031,000
Federal | 2033
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												57,363,000
Investment Tax Credit Carryforward												45,606,000
Federal | 2034
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												106,899,000
Investment Tax Credit Carryforward												37,699,000
Federal | 2035
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												51,308,000
Investment Tax Credit Carryforward												45,005,000
Federal | 2036
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												72,199,000
Investment Tax Credit Carryforward												11,744,000
Federal | 2037
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												75,606,000
Investment Tax Credit Carryforward												636,000
Federal | 2038
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												0
Investment Tax Credit Carryforward												93,000
State
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												424,241,000
State | 2031
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												3,142,000
State | 2032
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												17,982,000
State | 2033
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												35,232,000
State | 2034
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												28,853,000
State | 2035
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												9,956,000
State | 2036
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												170,497,000
State | 2037
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												89,714,000
State | 2038
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												68,865,000
South Jersey Gas Company
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at Statutory Rate									22,966,000	41,390,000	37,944,000
Increase (Decrease) Resulting from:
State Income Taxes									5,220,000	5,955,000	4,096,000
ESOP Dividend									(712,000)	(1,182,000)	(1,170,000)
AFUDC									(1,126,000)	(1,446,000)	(900,000)
Research and Development Credits									0	0	(613,000)
Other - Net									65,000	983,000	9,000
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Continuing Operations	6,913,000	(2,818,000)	482,000	21,836,000	18,046,000	(3,688,000)	1,431,000	29,911,000	26,413,000	45,700,000	39,366,000
Current:
Federal									(12,766,000)	(33,012,000)	0
State									0	0	(1,614,000)
Total Current									(12,766,000)	(33,012,000)	(1,614,000)
Deferred:
Federal									32,571,000	69,550,000	33,064,000
State									6,608,000	9,162,000	7,916,000
Total Deferred									39,179,000	78,712,000	40,980,000
Continuing Operations	6,913,000	$ (2,818,000)	$ 482,000	21,836,000	18,046,000	$ (3,688,000)	$ 1,431,000	29,911,000	26,413,000	45,700,000	39,366,000
Deferred Tax Assets:
Conservation Incentive Program												1,701,000	0
Net Operating Loss and Tax Credits												60,986,000	73,785,000
Deferred State Tax												16,754,000	14,688,000
Income Taxes Recoverable Through Rates												67,372,000	76,426,000
Pension & Other Post Retirement Benefits												16,699,000	15,031,000
Deferred Revenues												5,906,000	6,066,000
Provision for Uncollectibles												3,776,000	3,811,000
Other												2,599,000	2,413,000
Total Deferred Tax Asset												175,793,000	192,220,000
Deferred Tax Liabilities:
Book versus Tax Basis of Property												395,371,000	386,642,000
Deferred Gas Costs - Net												23,642,000	10,254,000
Environmental Remediation												40,753,000	31,637,000
Deferred Regulatory Costs												5,061,000	3,554,000
Budget Billing - Customer Accounts												4,550,000	4,043,000
Deferred Pension & Other Post Retirement Benefits												21,870,000	21,349,000
Section 461 Prepayments												1,081,000	866,000
Conservation Incentive Program												0	7,721,000
Other												9,351,000	6,900,000
Total Deferred Tax Liability												501,679,000	472,966,000
Deferred Tax Liability - Net												325,886,000	280,746,000
Income taxes due to or from related party												0	0
Research and development credits												2,700,000
Unrecognized tax benefits	1,063,000			1,361,000	1,361,000			1,361,000	1,361,000	1,361,000	559,000	1,063,000	1,361,000	1,361,000
Accrued interest and penalties on unrecognized tax benefits												800,000	700,000	$ 700,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance (beginning)				$ 1,361,000				$ 1,361,000	1,361,000	1,361,000	559,000
Increase as a result of tax positions taken in prior years									0	0	802,000
Decrease in prior year positions									(298,000)	0	0
Balance (ending)	$ 1,063,000				$ 1,361,000				$ 1,063,000	1,361,000	$ 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												200,000,000	261,100,000
South Jersey Gas Company | State
Deferred Tax Liabilities:
Net Operating Loss Carryforwards												$ 207,900,000	$ 208,800,000