FINANCIAL INSTRUMENTS - Cash, Cash Equivalents and Restricted Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents	$ 10,339	$ 6,417
Restricted Investments	21,694	21,964
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	32,033	28,381	$ 18,009	$ 31,679
SJG
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents	2,560	2,678
Restricted Investments	5,086	4,073
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 7,646	$ 6,751	$ 3,224	$ 3,262