REVENUE Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 317,917	$ 337,502	$ 243,395	$ 202,379
Unbilled Revenues	68,155	79,538	62,601	73,377
SJG Utility Operations
Disaggregation of Revenue [Line Items]
Accounts Receivable	146,185	101,572	50,012	78,571
Long-Term Receivables	26,428	25,531
Unbilled Revenues	38,292	$ 43,271	(10,693)	$ 54,980
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Accounts Receivable	(19,585)		41,016
Unbilled Revenues	(11,383)		(10,776)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09 | SJG Utility Operations
Disaggregation of Revenue [Line Items]
Accounts Receivable	44,613		128,583
Unbilled Revenues	$ (4,979)		$ 44,287