Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Revenues	$ 589,583	$ 302,480	$ 227,330	$ 521,945	$ 345,738	$ 227,127	$ 244,374	$ 425,829	$ 1,641,338	$ 1,243,068	$ 1,036,500
Expenses:
Cost of Sales - (Excluding depreciation and amortization)	393,432	233,112	145,796	283,068	210,585	168,815	179,684	287,143
Operations, Impairment Charges, Net Gains on Sale of Assets, Depreciation and Maintenance Including Fixed Charges (See Note 1)	133,121	131,899	208,384	92,540	152,091	121,439	77,504	84,496
Income Taxes	12,767	(16,649)	(31,972)	36,415	(16,498)	(24,765)	(5,544)	21,870	561	(24,937)	54,151
Energy and Other Taxes	3,260	2,595	1,243	2,439	1,348	1,517	1,551	2,071	9,537	6,487	6,342
Total Expenses	542,580	350,957	323,451	414,462	347,526	267,006	253,195	395,580
Other Income and Expense (See Note 1)	(971)	2,835	2,328	3,823	5,797	2,331	1,209	7,498
Income (Loss) from Continuing Operations	46,032	(45,642)	(93,793)	111,306	4,009	(37,548)	(7,612)	37,747	17,903	(3,404)	119,061
Loss from Discontinued Operations - (Net of tax benefit)	(105)	(43)	(26)	(66)	36	(45)	(47)	(30)	(240)	(86)	(251)
Net Income (Loss)	$ 45,927	$ (45,685)	$ (93,819)	$ 111,240	$ 4,045	$ (37,593)	$ (7,659)	$ 37,717	$ 17,663	$ (3,490)	$ 118,810
Basic Earnings Per Common Share:
Continuing Operations (in USD per share)	$ 0.54	$ (0.53)	$ (1.12)	$ 1.40	$ 0.05	$ (0.47)	$ (0.10)	$ 0.47	$ 0.21	$ (0.04)	$ 1.56
Discontinued Operations (in USD per share)	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Basic Earnings (Loss) per Common Share (in USD per share)	$ 0.54	$ (0.53)	$ (1.12)	$ 1.40	$ 0.05	$ (0.47)	$ (0.10)	$ 0.47	$ 0.21	$ (0.04)	$ 1.56
Average Shares of Common Stock Outstanding - Basic (in shares)	85,506	85,506	84,080	79,595	79,549	79,549	79,549	79,519	83,693	79,541	76,362
Diluted Earnings Per Common Share:
Continuing Operations (in USD per share)	$ 0.53	$ (0.53)	$ (1.12)	$ 1.40	$ 0.05	$ (0.47)	$ (0.10)	$ 0.47	$ 0.21	$ (0.04)	$ 1.56
Discontinued Operations (in USD per share)	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Diluted Earnings (Loss) per Common Share (in USD per share)	$ 0.53	$ (0.53)	$ (1.12)	$ 1.40	$ 0.05	$ (0.47)	$ (0.10)	$ 0.47	$ 0.21	$ (0.04)	$ 1.56
Average Shares of Common Stock Outstanding - Diluted (in shares)	86,389	85,506	84,080	79,724	79,705	79,549	79,549	79,641	84,471	79,541	76,475
South Jersey Gas Company
Operating Revenues	$ 180,369	$ 56,371	$ 76,801	$ 234,459	$ 170,434	$ 66,755	$ 83,251	$ 196,814	$ 548,000	$ 517,254	$ 461,055
Expenses:
Cost of Sales - (Excluding depreciation and amortization)	84,383	16,079	19,379	89,808	68,865	29,499	33,644	72,424	209,649	204,432	174,390
Operations, Impairment Charges, Net Gains on Sale of Assets, Depreciation and Maintenance Including Fixed Charges (See Note 1)	63,386	53,239	55,480	57,323	54,221	46,877	46,077	47,748
Income Taxes	6,913	(2,818)	482	21,836	18,046	(3,688)	1,431	29,911	26,413	45,700	39,366
Energy and Other Taxes	1,505	988	498	1,255	697	865	872	1,295	4,246	3,729	3,620
Total Expenses	156,187	67,488	75,839	170,222	141,829	73,553	82,024	151,378
Other Income and Expense (See Note 1)	(573)	2,141	607	2,510	979	1,027	1,039	1,042
Net Income (Loss)	$ 23,609	$ (8,976)	$ 1,569	$ 66,747	$ 29,584	$ (5,771)	$ 2,266	$ 46,478	$ 82,949	$ 72,557	$ 69,045