ACCUMULATED OTHER COMPREHENSIVE LOSS (AOCL) - SUMMARY OF CHANGES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 1,666,876	$ 1,423,785	$ 1,267,022
Other Comprehensive Income (Loss) - Net of Tax	11,487	(5,658)	(6,463)
Ending balance	1,999,441	1,666,876	1,423,785
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(38,216)	(32,558)	(26,095)
Other comprehensive income (loss) before reclassifications	11,455	(5,692)	(6,498)
Amounts reclassified from AOCL	32	34	35
Other Comprehensive Income (Loss) - Net of Tax	11,487	(5,658)	(6,463)
Ending balance	(26,729)	(38,216)	(32,558)
Postretirement Liability Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(37,816)	(32,124)	(25,626)
Other comprehensive income (loss) before reclassifications	11,455	(5,692)	(6,498)
Amounts reclassified from AOCL	0	0	0
Other Comprehensive Income (Loss) - Net of Tax	11,455	(5,692)	(6,498)
Ending balance	(26,361)	(37,816)	(32,124)
Unrealized Gain (Loss) on Derivatives-Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(293)	(327)	(362)
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified from AOCL	32	34	35
Other Comprehensive Income (Loss) - Net of Tax	32	34	35
Ending balance	(261)	(293)	(327)
Unrealized Gain (Loss) on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(10)	(10)	(10)
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified from AOCL	0	0	0
Other Comprehensive Income (Loss) - Net of Tax	0	0	0
Ending balance	(10)	(10)	(10)
Other Comprehensive Income (Loss) of Affiliated Companies
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(97)	(97)	(97)
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified from AOCL	0	0	0
Other Comprehensive Income (Loss) - Net of Tax	0	0	0
Ending balance	(97)	(97)	(97)
South Jersey Gas Company
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	8,598	(3,765)	(5,553)
Amounts reclassified from AOCL	32	34	35
Other Comprehensive Income (Loss) - Net of Tax	8,630	(3,731)	(5,518)
South Jersey Gas Company | Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(31,606)	(27,875)	(22,357)
Other Comprehensive Income (Loss) - Net of Tax	8,630	(3,731)	(5,518)
Ending balance	(22,976)	(31,606)	(27,875)
South Jersey Gas Company | Postretirement Liability Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(31,219)	(27,454)	(21,901)
Other comprehensive income (loss) before reclassifications	8,598	(3,765)	(5,553)
Amounts reclassified from AOCL	0	0	0
Other Comprehensive Income (Loss) - Net of Tax	8,598	(3,765)	(5,553)
Ending balance	(22,621)	(31,219)	(27,454)
South Jersey Gas Company | Unrealized Gain (Loss) on Derivatives-Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(387)	(421)	(456)
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified from AOCL	32	34	35
Other Comprehensive Income (Loss) - Net of Tax	32	34	35
Ending balance	$ (355)	$ (387)	$ (421)