DERIVATIVE INSTRUMENTS - Fair Value of all Derivative Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Assets	$ 53,609	$ 80,893
Liabilities	39,088	74,652
South Jersey Gas Company
Derivatives, Fair Value [Line Items]
Assets	7,998	5,807
Liabilities	9,475	8,737
Commodity Contract
Derivatives, Fair Value [Line Items]
Assets	53,609	80,893
Liabilities	0	0
Commodity Contract | South Jersey Gas Company
Derivatives, Fair Value [Line Items]
Assets	7,998	5,807
Liabilities	0	0
Derivatives not designated as hedging instruments under GAAP
Derivatives, Fair Value [Line Items]
Assets	53,609	80,893
Liabilities	39,088	74,652
Derivatives not designated as hedging instruments under GAAP | South Jersey Gas Company
Derivatives, Fair Value [Line Items]
Assets	7,998	5,807
Liabilities	9,475	8,737
Derivatives not designated as hedging instruments under GAAP | Commodity Contract | Derivatives - Energy Related - Current
Derivatives, Fair Value [Line Items]
Assets	46,361	72,391
Liabilities	23,082	60,082
Derivatives not designated as hedging instruments under GAAP | Commodity Contract | Derivatives - Energy Related - Current | South Jersey Gas Company
Derivatives, Fair Value [Line Items]
Assets	7,998	5,434
Liabilities	1,881	1,372
Derivatives not designated as hedging instruments under GAAP | Commodity Contract | Derivatives - Energy Related - Non-Current
Derivatives, Fair Value [Line Items]
Assets	7,248	8,502
Liabilities	4,660	4,540
Derivatives not designated as hedging instruments under GAAP | Commodity Contract | Derivatives - Energy Related - Non-Current | South Jersey Gas Company
Derivatives, Fair Value [Line Items]
Assets	0	373
Liabilities	297	0
Derivatives not designated as hedging instruments under GAAP | Interest rate contracts | Derivatives - Other - Current
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	787	681
Derivatives not designated as hedging instruments under GAAP | Interest rate contracts | Derivatives - Other - Current | South Jersey Gas Company
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	382	386
Derivatives not designated as hedging instruments under GAAP | Interest rate contracts | Derivatives - Other - Noncurrent
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	10,559	9,349
Derivatives not designated as hedging instruments under GAAP | Interest rate contracts | Derivatives - Other - Noncurrent | South Jersey Gas Company
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	$ 6,915	$ 6,979