FINANCIAL INSTRUMENTS - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 42,233	$ 30,410	$ 30,582	$ 19,829
Provision for expected credit losses	2,375	5,416	7,621	19,994
Regulated assets	(293)	0	8,982	0
Recoveries of accounts previously written off	414	126	772	688
Uncollectible accounts written off	(1,664)	(2,935)	(4,892)	(7,494)
Balance at end of period	43,065	33,017	43,065	33,017
SJG
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	21,706	14,472	17,359	14,032
Provision for expected credit losses	1,411	4,783	5,529	8,255
Regulated assets	1,059	0	3,030	0
Recoveries of accounts previously written off	400	4	503	295
Uncollectible accounts written off	(702)	(2,422)	(2,547)	(5,745)
Balance at end of period	$ 23,874	$ 16,837	$ 23,874	$ 16,837