FINANCIAL INSTRUMENTS - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 35,855	$ 23,533	$ 30,582	$ 19,829
Provision for expected credit losses	2,837	9,715	5,246	14,578
Regulated assets	5,141	0	9,275	0
Recoveries of accounts previously written off	128	319	358	562
Uncollectible accounts written off	(1,728)	(3,157)	(3,228)	(4,559)
Balance at end of period	42,233	30,410	42,233	30,410
SJG
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	20,473	14,902	17,359	14,032
Provision for expected credit losses	2,358	1,608	4,118	3,472
Regulated assets	(223)	0	1,971	0
Recoveries of accounts previously written off	(24)	159	103	291
Uncollectible accounts written off	(878)	(2,197)	(1,845)	(3,323)
Balance at end of period	$ 21,706	$ 14,472	$ 21,706	$ 14,472