REVENUE Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 220,561	$ 202,379
Unbilled Revenues	29,313	73,377
SJG Utility Operations
Disaggregation of Revenue [Line Items]
Accounts Receivable	72,010	78,571
Unbilled Revenues	7,995	$ 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	18,182
Unbilled Revenues	(44,064)
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	(6,561)
Unbilled Revenues	$ (46,985)