SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - PPE Utility (Details) $ in Thousands	Dec. 31, 2020 USD ($) project	Dec. 31, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Production Plant	$ 1,334	$ 1,334
Storage Plant	90,294	84,611
Transmission Plant	338,981	332,049
Distribution Plant	4,330,797	3,973,466
General Plant	428,737	310,785
Other Plant	1,955	1,955
Utility Plant In Service	5,192,098	4,704,200
Construction Work In Progress	73,563	201,150
Total Utility Plant	5,265,661	4,905,350
Nonutility Property and Equipment	$ 147,764	25,991
Number of solar energy sites previously classified as Assets Held for Sale | project	2
Solar Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	$ 40,380	0
Fuel Cell Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	80,546	0
Other Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	26,838	25,991
South Jersey Gas Company
Property, Plant and Equipment [Line Items]
Production Plant	25	25
Storage Plant	61,971	61,936
Transmission Plant	311,272	305,459
Distribution Plant	2,705,893	2,441,342
General Plant	265,185	238,379
Other Plant	1,855	1,855
Utility Plant In Service	3,346,201	3,048,996
Construction Work In Progress	41,630	105,740
Total Utility Plant	3,387,831	3,154,736
Nonutility Property and Equipment	0	0
South Jersey Gas Company | Solar Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	0	0
South Jersey Gas Company | Fuel Cell Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	0	0
South Jersey Gas Company | Other Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	$ 0	$ 0