SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - PPE Utility (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Production Plant	$ 1,281	$ 296
Storage Plant	92,769	61,909
Transmission Plant	326,906	258,598
Distribution Plant	3,466,101	2,044,421
General Plant	303,219	175,599
Other Plant	1,964	1,855
Utility Plant In Service	4,192,240	2,542,678
Construction Work In Progress	148,873	109,566
Total Utility Plant	4,341,113	2,652,244
Nonutility Property and Equipment	152,232	741,027
Solar Assets (A)
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	0	582,379
Cogeneration Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	126,228	125,614
Other Assets
Property, Plant and Equipment [Line Items]
Nonutility Property and Equipment	26,004	33,034
South Jersey Gas Company
Property, Plant and Equipment [Line Items]
Production Plant	296	296
Storage Plant	61,996	61,909
Transmission Plant	306,654	258,598
Distribution Plant	2,212,831	2,044,421
General Plant	241,095	175,599
Other Plant	1,855	1,855
Utility Plant In Service	2,824,727	2,542,678
Construction Work In Progress	82,475	109,566
Total Utility Plant	2,907,202	2,652,244
Nonutility Property and Equipment	0	0
South Jersey Gas Company | Solar Assets (A)
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