SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Part 2 (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 31, 2019
Regulatory Assets [Abstract]
Cash received for bond issuance		$ 30,000
Amortization period of other regulatory expense [Abstract]
Depreciation and salary 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		$ 6,891	$ 7,254
Summary of other deferred assets net of amortization [Abstract]
Investment in Co Bank		3,968	3,610
Other		289	321
Other deferred assets		4,257	3,931
Impairment or Disposal of Long-Lived Assets [Abstract]
Impairment		0	0	$ 0
Regulatory Liabilities [Line Items]
Decrease in the net deferred income tax liability			24,300	23,500
Net regulatory liability amount			22,800	$ 22,500
Regulatory Liabilities		$ 22,246	22,813
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]
Regulatory rate proceedings		5 years
Delaware [Member]
Amortization period of other regulatory expense [Abstract]
Regulatory 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
Artesian Water [Member]
Regulatory Assets [Abstract]
Contributions to postretirement benefit plan		23
Postretirement Benefit Obligation [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	52
Utility Plant Retirement Cost Obligation [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		247	319
Deferred Income Taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		21,999	22,442
Postretirement Benefit Obligation [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		51	74
Deferred Income Taxes [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		386	401
Expense Of Rate Case Studies [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		27	22
Debt Related Costs [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		5,556	5,815
Goodwill [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		288	295
Deferred Acquisition and Franchise Costs [Member]
Regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net		583	$ 647
Mountain Hill [Member]
Summary of other deferred assets net of amortization [Abstract]
Other		$ 200