SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Regulatory Assets (Details) - USD ($)			1 Months Ended	12 Months Ended
	May 04, 2016	Dec. 18, 2015	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 09, 2015
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
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net				$ 3,374,000	$ 4,176,000
Summary of other deferred assets net of amortization [Abstract]
Investment in Co Bank				3,198,000	3,023,000
Other				386,000	421,000
Other deferred assets				3,584,000	3,444,000
Stock Compensation Plans [Abstract]
Number of share authorize under equity compensation plan (in shares)							331,500
Compensation costs	$ 92,000	$ 137,000		92,000	183,000	$ 135,000
Unrecognized expense related to non-vested awards of restricted shares granted				$ 47,000
Summary of fair value of each option grant is estimated using the Black-Scholes-Merton option pricing model [Abstract]
Expected Dividend Yield						3.88%
Expected Stock Price Volatility						26.50%
Weighted Average Risk-Free Interest Rate						2.24%
Weighted Average Expected Life of Options						7 years 6 months 7 days
Base period for calculation of expected dividend yield				12 months
Shares granted as restricted stock awards	5,000
Shares issued as fully vested unrestricted stock awards		5,000
Fair market value (in dollars per share)	$ 27.70	$ 27.38
Award vesting period	1 year
Accounts Receivable [Abstract]
Expense related to allowance for doubtful accounts				$ 200,000	200,000
Summary of changes in entity's accounts receivable [Abstract]
Gross accounts receivable				8,059,000	6,627,000	$ 5,315,000
Less allowance for doubtful accounts				263,000	277,000	250,000
Net accounts receivable				7,796,000	6,350,000	5,065,000
Summary of allowance for doubtful accounts [Abstract]
Beginning balance			$ 263,000	277,000	250,000	221,000
Allowance adjustments				195,000	205,000	194,000
Recoveries				64,000	53,000	64,000
Write off of uncollectible accounts				(273,000)	(231,000)	(229,000)
Ending balance				$ 263,000	277,000	250,000
Cash and Cash Equivalents [Abstract]
Maximum maturity period of temporary cash investments considered as cash equivalents				3 months
Minimum [Member]
Amortization period of other regulatory expense [Abstract]
Amortization period of debt issuance cost				10 years
Summary of fair value of each option grant is estimated using the Black-Scholes-Merton option pricing model [Abstract]
Period for risk free interest rate base on treasury constant maturity rate				7 years
Minimum [Member] | Subsequent Event [Member]
Amortization period of other regulatory expense [Abstract]
Amortization period of debt issuance cost			15 years
Maximum [Member]
Amortization period of other regulatory expense [Abstract]
Amortization period of debt issuance cost				30 years
Summary of fair value of each option grant is estimated using the Black-Scholes-Merton option pricing model [Abstract]
Period for risk free interest rate base on treasury constant maturity rate				10 years
Maximum [Member] | Subsequent Event [Member]
Amortization period of other regulatory expense [Abstract]
Amortization period of debt issuance cost			25 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
Artesian Water [Member]
Regulatory Assets [Abstract]
Contributions to postretirement benefit plan				$ 81,000
Mountain Hill [Member]
Summary of other deferred assets net of amortization [Abstract]
Other				300,000
Postretirement Benefit Obligation [Member]
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net				186,000	329,000
Deferred Income Taxes [Member]
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net				431,000	446,000
Expense of Rate and Regulatory Proceedings [Member]
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net				116,000	616,000
Debt Issuance Costs [Member]
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net				1,648,000	1,747,000
Goodwill [Member]
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net				310,000	318,000
Deferred Acquisition and Franchise Costs [Member]
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net				683,000	720,000
Regulatory Assets, Net [Member]
Summary of regulatory assets net of amortization, comprise [Abstract]
Regulatory assets, net					4,176,000
CIAC and Other [Member]
Summary of changes in entity's accounts receivable [Abstract]
Contractual Amounts of Contributions In Aid of Construction Due from Developers And Other				2,622,000	1,610,000	1,295,000
Customer accounts receivable - water [Member]
Summary of changes in entity's accounts receivable [Abstract]
Gross accounts receivable				$ 5,437,000	$ 5,017,000	$ 4,020,000
Federal [Member]
Income Tax Contingency [Line Items]
Open tax year				2015
Federal [Member] | Internal Revenue Service (IRS) [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Open tax year				2012
Federal [Member] | Internal Revenue Service (IRS) [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Open tax year				2014
State [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Open tax year				2013
State [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Open tax year				2015