SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Assets and Liabilities Held For Sale (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Assets Held for Sale:
Current Assets	$ 39,829,000	$ 143,440,000
Liabilities Held for Sale:
Current Liabilities	5,804,000	6,043,000
Assets held for sale | SJG
Assets Held for Sale:
Total Assets Held for Sale	0	0
Liabilities Held for Sale:
Total Liabilities Held for Sale	0	0
Assets held for sale | MTF, ACB, and ELK
Assets Held for Sale:
Current Assets	0	5,365,000
Net Utility Plant	19,293,000	18,692,000
Net Nonutility Property, Plant & Equipment	19,993,000	110,400,000
Goodwill	59,000	59,000
Regulatory Assets	455,000	415,000
Other Noncurrent Assets	29,000	8,509,000
Total Assets Held for Sale	39,829,000	143,440,000
Liabilities Held for Sale:
Current Liabilities	0	916,000
Asset Retirement Obligations	2,609,000	2,515,000
Regulatory Liabilities	3,025,000	2,583,000
Other Noncurrent Liabilities	170,000	29,000
Total Liabilities Held for Sale	$ 5,804,000	$ 6,043,000