DERIVATIVE INSTRUMENTS (Details)	Dec. 31, 2018 USD ($)
South Jersey Industries Inc. | Interest Rate Swap, 20,000,000 Contract 1
Derivative [Line Items]
Notional Amount	$ 20,000,000
Fixed Interest Rate	3.049%
South Jersey Industries Inc. | Interest Rate Swap, 20,000,000 Contract 2
Derivative [Line Items]
Notional Amount	$ 20,000,000
Fixed Interest Rate	3.049%
South Jersey Industries Inc. | Interest Rate Swap, 10,000,000
Derivative [Line Items]
Notional Amount	$ 10,000,000
Fixed Interest Rate	3.049%
South Jersey Gas Company | Interest Rate Swap, 12,500,000, Contract 1
Derivative [Line Items]
Notional Amount	$ 12,500,000
Fixed Interest Rate	3.53%
South Jersey Gas Company | Interest Rate Swap, 12,500,000, Contract 2
Derivative [Line Items]
Notional Amount	$ 12,500,000
Fixed Interest Rate	3.43%