DERIVATIVE INSTRUMENTS - FAIR VALUES OF ALL DERIVATIVE INSTRUMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Energy-related commodity contracts
Derivatives, Fair Value [Line Items]
Assets	$ 48,374	$ 60,135
Liabilities	0	0
Derivatives not designated as hedging instruments under GAAP
Derivatives, Fair Value [Line Items]
Assets	48,374	60,135
Liabilities	41,891	62,831
Derivatives not designated as hedging instruments under GAAP | Energy-related commodity contracts | Derivatives – Energy Related – Current
Derivatives, Fair Value [Line Items]
Assets	41,439	52,892
Liabilities	27,006	41,965
Derivatives not designated as hedging instruments under GAAP | Energy-related commodity contracts | Derivatives – Energy Related – Noncurrent
Derivatives, Fair Value [Line Items]
Assets	6,935	7,243
Liabilities	4,947	8,206
Derivatives not designated as hedging instruments under GAAP | Interest rate contract | Derivatives - Other - Current
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	659	1,155
Derivatives not designated as hedging instruments under GAAP | Interest rate contract | Derivatives - Other - Noncurrent
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	9,279	11,505
South Jersey Gas Company | Energy-related commodity contracts
Derivatives, Fair Value [Line Items]
Assets	4,140	16,909
Liabilities	0	0
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP
Derivatives, Fair Value [Line Items]
Assets	4,140	16,909
Liabilities	12,996	22,622
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP | Energy-related commodity contracts | Derivatives – Energy Related – Current
Derivatives, Fair Value [Line Items]
Assets	4,053	16,904
Liabilities	2,868	14,671
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP | Energy-related commodity contracts | Derivatives – Energy Related – Noncurrent
Derivatives, Fair Value [Line Items]
Assets	87	5
Liabilities	190	95
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	659	488
South Jersey Gas Company | Derivatives not designated as hedging instruments under GAAP | Interest rate contract | Derivatives - Other - Noncurrent
Derivatives, Fair Value [Line Items]
Assets	0	0
Liabilities	$ 9,279	$ 7,368