DERIVATIVE INSTRUMENTS - FAIR VALUES OF ALL DERIVATIVE INSTRUMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Commodity contract
Derivatives, Fair Value [Line Items]
Assets	$ 61,190	$ 48,127
Liabilities	0	0
Derivatives not designated as hedging instruments under GAAP
Derivatives, Fair Value [Line Items]
Assets	61,190	48,127
Liabilities	39,263	63,333
Derivatives not designated as hedging instruments under GAAP | Commodity contract | Derivatives – Energy Related – Current
Derivatives, Fair Value [Line Items]
Assets	54,021	42,139
Liabilities	24,134	46,938
Derivatives not designated as hedging instruments under GAAP | Commodity contract | Derivatives – Energy Related – Non-Current
Derivatives, Fair Value [Line Items]
Assets	7,169	5,988
Liabilities	7,256	6,025
Derivatives not designated as hedging instruments under GAAP | Interest rate contract | Derivatives - Other - Current
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	588	748
Derivatives not designated as hedging instruments under GAAP | Interest rate contract | Derivatives - Other - Non-Current
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	7,285	9,622
South Jersey Gas Company | Commodity contract
Derivatives, Fair Value [Line Items]
Assets	5,479	7,332
Liabilities	0	0
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP
Derivatives, Fair Value [Line Items]
Assets	5,479	7,332
Liabilities	8,056	16,468
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP | Commodity contract | Derivatives – Energy Related – Current
Derivatives, Fair Value [Line Items]
Assets	5,464	7,327
Liabilities	2,146	9,270
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP | Commodity contract | Derivatives – Energy Related – Non-Current
Derivatives, Fair Value [Line Items]
Assets	15	5
Liabilities	43	170
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP | Interest rate contract | Derivatives - Other - Current
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	343	389
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP | Interest rate contract | Derivatives - Other - Non-Current
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	$ 5,524	$ 6,639