SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Solar Asset Sale (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) project	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number Of Projects Closed | project	4
Number of Solar Energy Sites | project	4
Assets held for sale	$ 37,532,000		$ 59,588,000
Impairment charge		$ 0
SJG Utility Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge	0	$ 0
Regulatory assets	454,542,000		$ 492,365,000
Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business	16,100,000
Gain (loss) on sale of assets	100,000
Assets Held-for-sale, Long Lived, Fair Value Disclosure	$ 37,500,000