FINANCIAL INSTRUMENTS - CASH, CASH EQUIVALENTS, AND RESTRICTED CASH (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents	$ 34,045	$ 6,417
Restricted Investments	7,786	21,964
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	41,831	28,381	$ 31,679	$ 39,695
South Jersey Gas Company
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents	1,598	2,678
Restricted Investments	4,826	4,073
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 6,424	$ 6,751	$ 3,262	$ 4,619