FINANCIAL INSTRUMENTS - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	$ 23,533	$ 19,829
Provision for expected credit losses	9,715	14,578
Recoveries of accounts previously written off	319	562
Uncollectible accounts written off	(3,157)	(4,559)
Balance at end of period	30,410	30,410
SJG
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	14,902	14,032
Provision for expected credit losses	1,608	3,472
Recoveries of accounts previously written off	159	291
Uncollectible accounts written off	(2,197)	(3,323)
Balance at end of period	$ 14,472	$ 14,472