SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Part 2 (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Aug. 03, 2020	Jan. 31, 2019
Regulatory Assets [Abstract]
Cash received for bond issuance		$ 30,000
Amortization period of other regulatory expense [Abstract]
Deferred contract costs and other		5 years
Rate case studies		5 years
Goodwill		50 years
Deferred acquisition costs		20 years
Franchise costs		80 years
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		$ 6,321	$ 6,473
Summary of other deferred assets net of amortization [Abstract]
Investment in Co Bank		4,850	4,374
Other deferred assets/goodwill		247	935				$ 623
Other		5,097	5,309
Regulatory adjustment		1,500
Impairment or Disposal of Long-Lived Assets [Abstract]
Impairment		0	$ 0	$ 0
Contributions in Aid of Construction [Abstract]
Refund for contributions in aid of construction due to tax status change		$ 3,200
Regulatory Liabilities [Line Items]
Federal corporate tax rate		21.00%	21.00%	21.00%		34.00%
Decrease in the net deferred income tax liability			$ 24,300		$ 24,300
Net regulatory liability amount			22,800		$ 22,800
Regulatory Liabilities		$ 21,260	21,681
Minimum [Member]
Amortization period of other regulatory expense [Abstract]
Amortization period of debt related cost	15 years
Maximum [Member]
Amortization period of other regulatory expense [Abstract]
Amortization period of debt related cost	30 years
Maryland [Member]
Amortization period of other regulatory expense [Abstract]
Rate proceedings		5 years
Delaware [Member]
Amortization period of other regulatory expense [Abstract]
Rate proceedings		2 years 6 months
DEPSC [Member]
Regulatory Liabilities [Line Items]
Net regulatory liability amount								$ 22,200
Regulatory liabilities, amortization period		49 years 6 months
MDPSC [Member]
Regulatory Liabilities [Line Items]
Net regulatory liability amount		$ 600	600
Utility Plant Retirement Cost Obligation [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		149	126
Deferred Income Taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		21,111	21,555
Deferred Income Taxes [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		355	370
Deferred Contract Costs and Other [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		288	46
Debt Related Costs [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		4,902	5,233
Goodwill [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		273	281
Deferred Acquisition and Franchise Costs [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		$ 503	$ 543