PENSION AND OTHER POSTRETIREMENT BENEFITS - CONTRIBUTIONS (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits		$ 3,200
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions To Defined Pension Plan	$ 10,000	0		$ 0
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019		21,690
2020		22,382
2021		22,517
2022		23,108
2023		23,883
2024- 2028		122,192
Employer contributions		2,704	$ 12,369
Other Postretirement Benefits
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019		5,873
2020		5,853
2021		5,811
2022		5,728
2023		5,561
2024- 2028		24,069
Employer contributions		2,796	2,806
Expected contribution to plan		3,600
Supplemental Employee Retirement Plan
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Employer contributions		2,700	2,400	2,300
Expected contribution to plan		3,600
South Jersey Gas Company | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions To Defined Pension Plan	$ 8,000	0		$ 0
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019		12,777
2020		13,265
2021		13,674
2022		14,207
2023		14,788
2024- 2028		79,003
Employer contributions		2,669	10,292
South Jersey Gas Company | Other Postretirement Benefits
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019		3,879
2020		3,888
2021		3,817
2022		3,739
2023		3,639
2024- 2028		15,444
Employer contributions		1,979	$ 2,259
ETG Utility Operations And ELK Utility Operations
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent		$ 5,100