REGULATORY LIABILITIES (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
REGULATORY LIABILITIES [Abstract]
Artesian Water contributed to its postretirement benefit plan	$ 9,300
Federal corporate tax rate	21.00%	34.00%
Decrease in the net deferred income tax liability	$ 23,500,000
Net regulatory liability amount	22,500,000
Regulatory Liabilities [Line Items]
Regulatory liabilities	23,202,000	$ 23,201,000
Postretirement Benefit Obligation [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	112,000	112,000
Utility Plant Retirement Cost Obligation [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	550,000	549,000
Deferred Income Taxes (related to TCJA) [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 22,540,000	$ 22,540,000