AFFILIATIONS, DISCONTINUED OPERATIONS AND RELATED-PARTY TRANSACTIONS - Summary of Financial Information for PennEast (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenues	$ 1,991,996	$ 1,541,383	$ 1,628,626
(Loss) Income from Continuing Operations	88,514	157,297	77,189
Net (Loss) Income	88,565	157,042	76,917
Net (Loss) Income Attributable to South Jersey Industries, Inc.	88,091	157,084	76,917
Statement of Financial Position [Abstract]
Current Assets	638,962	506,828
Current Liabilities	955,682	1,163,632
Noncurrent Liabilities	1,164,540	1,082,240
PennEast
Income Statement [Abstract]
Revenues	0	0	0
Gross Profit	0	0	0
(Loss) Income from Continuing Operations	(416,073)	34,663	32,291
Net (Loss) Income	(416,073)	34,663	32,291
Net (Loss) Income Attributable to South Jersey Industries, Inc.	(83,215)	6,933	6,458
Statement of Financial Position [Abstract]
Current Assets	1,216	3,079
Noncurrent Assets	45,000	456,205
Current Liabilities	479	2,789
Noncurrent Liabilities	500	0
Energenic
Income Statement [Abstract]
Revenues	143	144	144
Gross Profit	61	64	65
(Loss) Income from Continuing Operations	(16,628)	(3,797)	(3,795)
Net (Loss) Income	(16,628)	(3,797)	(3,795)
Net (Loss) Income Attributable to South Jersey Industries, Inc.	(8,314)	(1,898)	(1,898)
Statement of Financial Position [Abstract]
Current Assets	11,181	10,284
Noncurrent Assets	8,764	24,296
Current Liabilities	17,456	15,319
Noncurrent Liabilities	29,378	29,522
Affiliates
Income Statement [Abstract]
Revenues	136,819	77,266	94,570
Gross Profit	30,919	16,278	14,930
(Loss) Income from Continuing Operations	(424,006)	36,906	32,825
Net (Loss) Income	(424,006)	36,906	32,825
Net (Loss) Income Attributable to South Jersey Industries, Inc.	(90,961)	8,294	$ 7,314
Statement of Financial Position [Abstract]
Current Assets	67,160	38,286
Noncurrent Assets	113,685	505,846
Current Liabilities	40,214	30,586
Noncurrent Liabilities	$ 93,285	$ 49,737