PENSION AND OTHER POSTRETIREMENT BENEFITS - RECONCILIATIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amounts Recognized in the Statement of Financial Position Consist of:
Current Liabilities	$ (3,631)	$ (2,388)
Noncurrent Liabilities	(110,112)	(101,544)
South Jersey Gas Company
Amounts Recognized in the Statement of Financial Position Consist of:
Current Liabilities	(3,597)	(2,353)
Noncurrent Liabilities	(96,053)	(88,871)
Pension Benefits
Change in Benefit Obligations:
Benefit Obligation at Beginning of Year	316,289	278,288
Acquisition Opening Obligation	100,362	0
Service Cost	6,442	4,989	$ 4,843
Interest Cost	13,778	11,772	12,125
Actuarial Loss (Gain)	(26,274)	32,893
Retiree Contributions	0	0
Plan Amendments	7,394	0
Benefit Obligation at End of Year	402,156	316,289	278,288
Change in Plan Assets:
Fair Value of Plan Assets at Beginning of Year	216,065	189,542
Acquisition Beginning Fair Value	94,685	0
Actual Return on Plan Assets	(10,399)	25,807
Employer Contributions	2,704	12,369
Retiree Contributions	0	0
Benefits Paid	(15,835)	(11,653)
Fair Value of Plan Assets at End of Year	287,220	216,065	189,542
Funded Status at End of Year	(114,936)	(100,224)
Accrued Net Benefit Cost at End of Year	(115,083)	(100,089)
Amounts Recognized in the Statement of Financial Position Consist of:
Current Liabilities	(3,631)	(2,388)
Noncurrent Liabilities	(111,452)	(97,701)
Net Amount Recognized at End of Year	(115,083)	(100,089)
Amounts Recognized in Regulatory Assets Consist of:
Prior Service Costs	162	428
Net Actuarial Loss	67,377	64,541
Amount Recognized in Regulatory Assets	67,539	64,969	68,450
Amounts Recognized in Accumulated Other Comprehensive Loss Consist of (pre-tax):
Prior Service Costs	268	47
Net Actuarial Loss	42,257	53,885
Amount Recognized in Accumulated Other Comprehensive Loss	42,525	53,932	39,590
Projected benefit obligation	329,200	243,900
Accumulated benefit obligation	309,400	227,300
Benefits Paid	(15,835)	(11,653)
Pension Benefits | South Jersey Gas Company
Change in Benefit Obligations:
Benefit Obligation at Beginning of Year	269,066	236,356
Service Cost	5,073	4,303	4,144
Interest Cost	10,010	9,925	10,292
Actuarial Loss (Gain)	(13,009)	27,892
Retiree Contributions	0	0
Plan Amendments	4,169	0
Benefit Obligation at End of Year	264,823	269,066	236,356
Change in Plan Assets:
Fair Value of Plan Assets at Beginning of Year	174,277	154,729
Actual Return on Plan Assets	(6,175)	18,666
Employer Contributions	2,669	10,292
Retiree Contributions	0	0
Benefits Paid	(10,486)	(9,410)
Fair Value of Plan Assets at End of Year	160,285	174,277	154,729
Funded Status at End of Year	(104,538)	(94,789)
Amounts Recognized in the Statement of Financial Position Consist of:
Current Liabilities	(3,597)	(2,353)
Noncurrent Liabilities	(100,941)	(92,436)
Net Amount Recognized at End of Year	(104,538)	(94,789)
Amounts Recognized in Regulatory Assets Consist of:
Prior Service Costs	163	428
Net Actuarial Loss	65,330	64,541
Amount Recognized in Regulatory Assets	65,493	64,969	68,450
Amounts Recognized in Accumulated Other Comprehensive Loss Consist of (pre-tax):
Net Actuarial Loss	34,396	39,356
Amount Recognized in Accumulated Other Comprehensive Loss	34,396	39,356	24,102
Projected benefit obligation	188,100	197,000
Accumulated benefit obligation	176,800	183,500
Benefits Paid	(10,486)	(9,410)
Pension Benefits | Amounts Related to Unconsolidated Affiliate
Change in Plan Assets:
Funded Status at End of Year	(147)	135
Other Postretirement Benefits
Change in Benefit Obligations:
Benefit Obligation at Beginning of Year	62,283	60,350
Acquisition Opening Obligation	13,195	0
Service Cost	945	910	851
Interest Cost	2,430	2,418	2,615
Actuarial Loss (Gain)	(3,534)	1,411
Retiree Contributions	265	19
Plan Amendments	(3,012)	0
Benefit Obligation at End of Year	69,511	62,283	60,350
Change in Plan Assets:
Fair Value of Plan Assets at Beginning of Year	57,922	50,532
Acquisition Beginning Fair Value	15,659	0
Actual Return on Plan Assets	(3,050)	7,390
Employer Contributions	2,796	2,806
Retiree Contributions	265	19
Benefits Paid	(3,061)	(2,825)
Fair Value of Plan Assets at End of Year	70,531	57,922	50,532
Funded Status at End of Year	1,020	(4,361)
Accrued Net Benefit Cost at End of Year	1,340	(3,843)
Amounts Recognized in the Statement of Financial Position Consist of:
Current Liabilities	0	0
Noncurrent Liabilities	1,340	(3,843)
Net Amount Recognized at End of Year	1,340	(3,843)
Amounts Recognized in Regulatory Assets Consist of:
Prior Service Costs	(5,765)	(2,775)
Net Actuarial Loss	20,984	16,017
Amount Recognized in Regulatory Assets	15,219	13,242	17,243
Amounts Recognized in Accumulated Other Comprehensive Loss Consist of (pre-tax):
Prior Service Costs	(1,707)	(906)
Net Actuarial Loss	2,394	4,412
Amount Recognized in Accumulated Other Comprehensive Loss	687	3,506	2,821
Benefits Paid	(3,061)	(2,825)
Other Postretirement Benefits | South Jersey Gas Company
Change in Benefit Obligations:
Benefit Obligation at Beginning of Year	49,098	48,549
Service Cost	583	582	576
Interest Cost	1,698	1,897	2,120
Actuarial Loss (Gain)	(1,271)	328
Retiree Contributions	143	15
Plan Amendments	(3,247)	0
Benefit Obligation at End of Year	44,882	49,098	48,549
Change in Plan Assets:
Fair Value of Plan Assets at Beginning of Year	52,663	45,948
Actual Return on Plan Assets	(2,893)	6,715
Employer Contributions	1,979	2,259
Retiree Contributions	143	14
Benefits Paid	(2,122)	(2,273)
Fair Value of Plan Assets at End of Year	49,770	52,663	45,948
Funded Status at End of Year	4,888	3,565
Amounts Recognized in the Statement of Financial Position Consist of:
Current Liabilities	0	0
Noncurrent Liabilities	4,888	3,565
Net Amount Recognized at End of Year	4,888	3,565
Amounts Recognized in Regulatory Assets Consist of:
Prior Service Costs	(5,765)	(2,775)
Net Actuarial Loss	20,393	16,017
Amount Recognized in Regulatory Assets	14,628	13,242	17,243
Amounts Recognized in Accumulated Other Comprehensive Loss Consist of (pre-tax):
Net Actuarial Loss	0	0
Amount Recognized in Accumulated Other Comprehensive Loss	0	0	0
Benefits Paid	(2,122)	(2,273)
Other Postretirement Benefits | Amounts Related to Unconsolidated Affiliate
Change in Plan Assets:
Funded Status at End of Year	320	518
Supplemental Employee Retirement Plan
Change in Plan Assets:
Employer Contributions	2,700	2,400	2,300
Amounts Recognized in Accumulated Other Comprehensive Loss Consist of (pre-tax):
Projected benefit obligation	73,000	72,400
Accumulated benefit obligation	69,500	63,900
Supplemental Employee Retirement Plan | South Jersey Gas Company
Change in Benefit Obligations:
Retiree Contributions	3,861	2,235	$ 1,960
Amounts Recognized in Accumulated Other Comprehensive Loss Consist of (pre-tax):
Projected benefit obligation	72,600	72,000
Accumulated benefit obligation	$ 69,100	$ 63,600