FINANCIAL INSTRUMENTS - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 30,410	$ 19,829
Provision for expected credit losses	5,416	19,994
Recoveries of accounts previously written off	126	688
Uncollectible accounts written off	(2,935)	(7,494)
Balance at end of period	33,017	33,017
SJG
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	14,472	14,032
Provision for expected credit losses	4,783	8,255
Recoveries of accounts previously written off	4	295
Uncollectible accounts written off	(2,422)	(5,745)
Balance at end of period	$ 16,837	$ 16,837