DERIVATIVE INSTRUMENTS - Fair Value of all Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Energy-related Commodity Contracts
Derivatives, Fair Value [Line Items]
Assets	$ 239,587	$ 117,529
Liabilities	0	0
Energy-related Commodity Contracts | SJG
Derivatives, Fair Value [Line Items]
Assets	33,969	9,903
Liabilities	0	0
Derivatives not designated as hedging instruments under GAAP
Derivatives, Fair Value [Line Items]
Assets	239,587	117,529
Liabilities	202,025	84,081
Derivatives not designated as hedging instruments under GAAP | SJG
Derivatives, Fair Value [Line Items]
Assets	33,969	9,903
Liabilities	12,833	10,844
Derivatives not designated as hedging instruments under GAAP | Energy-related Commodity Contracts | Derivatives - Energy Related - Current
Derivatives, Fair Value [Line Items]
Assets	187,126	95,041
Liabilities	159,805	60,002
Derivatives not designated as hedging instruments under GAAP | Energy-related Commodity Contracts | Derivatives - Energy Related - Current | SJG
Derivatives, Fair Value [Line Items]
Assets	33,317	9,396
Liabilities	9,547	2,520
Derivatives not designated as hedging instruments under GAAP | Energy-related Commodity Contracts | Derivatives - Energy Related - Non-Current
Derivatives, Fair Value [Line Items]
Assets	52,461	22,488
Liabilities	39,359	16,079
Derivatives not designated as hedging instruments under GAAP | Energy-related Commodity Contracts | Derivatives - Energy Related - Non-Current | SJG
Derivatives, Fair Value [Line Items]
Assets	652	507
Liabilities	425	324
Derivatives not designated as hedging instruments under GAAP | Interest Rate Contracts | Derivatives - Other - Current
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	215	568
Derivatives not designated as hedging instruments under GAAP | Interest Rate Contracts | Derivatives - Other - Current | SJG
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	215	568
Derivatives not designated as hedging instruments under GAAP | Interest Rate Contracts | Derivatives - Other - Noncurrent
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	2,646	7,432
Derivatives not designated as hedging instruments under GAAP | Interest Rate Contracts | Derivatives - Other - Noncurrent | SJG
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	$ 2,646	$ 7,432