FAIR VALUE OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES - Changes in Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	$ 11,006	$ 17,574
Other Changes in Fair Value from Continuing and New Contracts, Net	5,477	9,403
Settlements	(5,063)	(7,999)
Balance at end of period	11,420	18,978
SJG
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period	3,385	5,035
Other Changes in Fair Value from Continuing and New Contracts, Net	3,391	4,806
Settlements	(3,385)	(5,035)
Balance at end of period	$ 3,391	$ 4,806