SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - PPE Utility (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Production Plant	$ 1,334	$ 1,281
Storage Plant	84,611	92,769
Transmission Plant	332,049	326,906
Distribution Plant	3,973,466	3,466,101
General Plant	310,785	303,219
Other Plant	1,955	1,964
Utility Plant In Service	4,704,200	4,192,240
Construction Work In Progress	201,150	148,873
Total Utility Plant	4,905,350	4,341,113
Nonutility Property and Equipment	25,991	152,232
Solar Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	0	0
Cogeneration Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	0	126,228
Other Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	25,991	26,004
South Jersey Gas Company
Property, Plant and Equipment [Line Items]
Production Plant	25	296
Storage Plant	61,936	61,996
Transmission Plant	305,459	306,654
Distribution Plant	2,441,342	2,212,831
General Plant	238,379	241,095
Other Plant	1,855	1,855
Utility Plant In Service	3,048,996	2,824,727
Construction Work In Progress	105,740	82,475
Total Utility Plant	3,154,736	2,907,202
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 | Cogeneration 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