FINANCIAL INSTRUMENTS - Cash, Cash Equivalents and Restricted Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents	$ 4,602	$ 30,030
Restricted Investments	16,271	1,649
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	20,873	31,679	$ 13,316	$ 39,695
SJG
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents	1,347	1,984
Restricted Investments	2,084	1,278
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 3,431	$ 3,262	$ 2,179	$ 4,619