Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation Allowance for Deferred Tax Assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 0
Charged to Costs and Expenses	7,392
Regulated Asset	0
Acquisition Adjustments	0
Charged to Other Accounts	0
Deductions	0
Balance at End of Period	7,392	$ 0
Provision for Uncollectible Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	19,829	18,842	$ 13,988
Charged to Costs and Expenses	9,558	10,432	7,977
Regulated Asset	10,953	0	0
Acquisition Adjustments	0	0	6,579
Charged to Other Accounts	909	(292)	(466)
Deductions	10,667	9,153	9,236
Balance at End of Period	30,582	19,829	18,842
South Jersey Gas Company | Provision for Uncollectible Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	14,032	13,643	13,799
Charged to Costs and Expenses	6,209	7,193	7,997
Regulated Asset	4,845	0	0
Charged to Other Accounts	424	(292)	(466)
Deductions	8,151	6,512	7,687
Balance at End of Period	$ 17,359	$ 14,032	$ 13,643