Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Revenues	$ 485,758	$ 261,549	$ 259,964	$ 534,112	$ 463,191	$ 261,203	$ 266,934	$ 637,298	$ 1,541,383	$ 1,628,626	$ 1,641,338
Expenses:
Cost of Sales - (Excluding depreciation and amortization)	269,185	176,029	147,653	266,068	273,873	190,366	165,341	402,387
Operations, Impairment Charges, Net Gains on Sale of Assets, Depreciation and Maintenance Including Fixed Charges	138,767	119,046	118,073	130,956	138,641	116,056	118,444	124,794
Income Taxes	8,939	(19,467)	(178)	33,370	11,683	(10,925)	(4,646)	24,949	22,664	21,061	561
Energy and Other Taxes	2,690	2,730	2,636	3,862	2,399	2,663	2,717	4,217	11,918	11,996	9,537
Total Expenses	419,581	278,338	268,184	434,256	426,596	298,160	281,856	556,347
Other Income and Expense	2,942	6,445	5,642	1,244	2,945	2,211	1,618	4,748
Income (Loss) from Continuing Operations	69,119	(10,344)	(2,578)	101,100	39,540	(34,746)	(13,304)	85,699	157,297	77,189	17,903
Loss from Discontinued Operations - (Net of tax benefit)	(77)	(58)	(61)	(59)	(56)	(59)	(95)	(62)	(255)	(272)	(240)
Net Income	$ 69,042	$ (10,402)	$ (2,639)	$ 101,041	$ 39,484	$ (34,805)	$ (13,399)	$ 85,637	$ 157,042	$ 76,917	$ 17,663
Basic Earnings (Loss) Per Common Share:
Continuing Operations (in USD per share)	$ 0.69	$ (0.10)	$ (0.03)	$ 1.09	$ 0.43	$ (0.38)	$ (0.14)	$ 0.94	$ 1.62	$ 0.84	$ 0.21
Discontinued Operations (in USD per share)	0	0	0	0	0	0	0	0	0	0	0
Net Income (in USD per share)	$ 0.69	$ (0.10)	$ (0.03)	$ 1.09	$ 0.43	$ (0.38)	$ (0.14)	$ 0.94	$ 1.62	$ 0.84	$ 0.21
Average Shares of Common Stock Outstanding - Basic (in shares)	100,590	100,587	93,712	92,445	92,130	92,392	92,389	91,332	96,854	92,130	83,693
Diluted Earnings Per Common Share:
Continuing Operations (in USD per share)	$ 0.69	$ (0.10)	$ (0.03)	$ 1.09	$ 0.43	$ (0.38)	$ (0.14)	$ 0.94	$ 1.62	$ 0.84	$ 0.21
Discontinued Operations (in USD per share)	0	0	0	0	0	0	0	0	0	0	0
Net Income (in USD per share)	$ 0.69	$ (0.10)	$ (0.03)	$ 1.09	$ 0.43	$ (0.38)	$ (0.14)	$ 0.94	$ 1.62	$ 0.84	$ 0.21
Average Shares of Common Stock Outstanding - Diluted (in shares)	100,780	100,587	93,712	92,556	92,253	92,392	92,389	91,432	96,995	92,253	84,471
South Jersey Gas Company
Operating Revenues	$ 177,721	$ 66,190	$ 87,182	$ 240,694	$ 172,721	$ 62,039	$ 62,268	$ 272,198	$ 571,787	$ 569,226	$ 548,000
Expenses:
Cost of Sales - (Excluding depreciation and amortization)	54,607	20,575	25,546	80,534	70,542	19,268	2,654	118,880	181,262	211,344	209,649
Operations, Impairment Charges, Net Gains on Sale of Assets, Depreciation and Maintenance Including Fixed Charges	68,624	58,772	58,853	61,442	62,412	57,771	56,141	60,832
Income Taxes	12,167	(3,293)	1,219	25,231	12,201	(3,747)	671	23,697	35,324	32,822	26,413
Energy and Other Taxes	1,108	1,194	1,070	1,615	584	1,159	1,154	1,989	$ 4,987	$ 4,886	$ 4,246
Total Expenses	136,506	77,248	86,688	168,822	145,739	74,451	60,620	205,398
Other Income and Expense	2,187	1,515	3,184	(1,350)	1,309	808	328	1,931
Net Income	$ 43,402	$ (9,543)	$ 3,678	$ 70,522	$ 28,291	$ (11,604)	$ 1,976	$ 68,731