FAIR VALUE OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES - Changes in Measurements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	$ 4,956	$ 12,251	$ 11,006	$ 17,574
Other Changes in Fair Value from Continuing and New Contracts, Net	(13,860)	(3,198)	(12,547)	3,819
Settlements	(1,222)	(2,644)	(8,585)	(14,984)
Balance at end of period	(10,126)	6,409	(10,126)	6,409
SJG
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	4,721	4,365	3,385	5,035
Other Changes in Fair Value from Continuing and New Contracts, Net	2,396	(61)	7,117	4,304
Settlements	0	0	(3,385)	(5,035)
Balance at end of period	$ 7,117	$ 4,304	$ 7,117	$ 4,304