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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Regulatory Assets (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
May 25, 2005
Regulatory Assets [Abstract]        
Amortization period of depreciation and salary study expenses five      
Goodwill amortization period 50 years      
Amortization period of deferred acquisition costs 20 years      
Amortization period of deferred franchise costs 80 years      
Summary of regulatory assets net of amortization, comprise [Abstract]        
Regulatory assets, net $ 2,561,000us-gaap_RegulatoryAssets $ 2,304,000us-gaap_RegulatoryAssets    
Summary of other deferred assets net of amortization [Abstract]        
Debt issuance cost 1,869,000us-gaap_DeferredFinanceCostsNet 1,989,000us-gaap_DeferredFinanceCostsNet    
Investment in Co Bank 2,851,000us-gaap_HeldToMaturitySecurities 2,680,000us-gaap_HeldToMaturitySecurities    
Other 461,000us-gaap_OtherDeferredCostsNet 503,000us-gaap_OtherDeferredCostsNet    
Other deferred assets 5,181,000us-gaap_OtherAssetsNoncurrent 5,172,000us-gaap_OtherAssetsNoncurrent    
Stock Compensation Plans [Abstract]        
Number of share authorize under equity compensation plan (in shares)       500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Compensation costs 135,000us-gaap_ShareBasedCompensation 123,000us-gaap_ShareBasedCompensation 108,000us-gaap_ShareBasedCompensation  
Summary of fair value of each option grant is estimated using the Black-Scholes-Merton option pricing model [Abstract]        
Dividend Yield (in hundredths) 3.88%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 3.63%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 4.18%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate  
Expected Volatility (in hundredths) 26.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 26.16%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 25.13%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate  
Risk Free Interest Rate (in hundredths) 2.24%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 1.68%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 1.87%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate  
Expected Term 7 years 6 months 7 days 9 years 4 months 28 days 9 years 5 months 19 days  
Base period for calculation of expected dividend yield 12 months      
Accounts Receivable [Abstract]        
Expense related to allowance for doubtful accounts 200,000artna_ExpenseRelatedToAllowanceForDoubtfulAccounts 200,000artna_ExpenseRelatedToAllowanceForDoubtfulAccounts    
Summary of changes in entity's accounts receivable [Abstract]        
Gross accounts receivable 5,315,000us-gaap_AccountsReceivableGrossCurrent 5,336,000us-gaap_AccountsReceivableGrossCurrent 5,969,000us-gaap_AccountsReceivableGrossCurrent  
Less allowance for doubtful accounts 250,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent 221,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent 241,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent  
Net accounts receivable 5,065,000us-gaap_AccountsReceivableNetCurrent 5,115,000us-gaap_AccountsReceivableNetCurrent 5,728,000us-gaap_AccountsReceivableNetCurrent  
Summary of allowance for doubtful accounts [Abstract]        
Beginning balance 221,000us-gaap_AllowanceForDoubtfulAccountsReceivable 241,000us-gaap_AllowanceForDoubtfulAccountsReceivable 216,000us-gaap_AllowanceForDoubtfulAccountsReceivable  
Allowance adjustments 194,000us-gaap_ProvisionForDoubtfulAccounts 180,000us-gaap_ProvisionForDoubtfulAccounts 215,000us-gaap_ProvisionForDoubtfulAccounts  
Recoveries 64,000us-gaap_AllowanceForDoubtfulAccountsReceivableRecoveries 115,000us-gaap_AllowanceForDoubtfulAccountsReceivableRecoveries 141,000us-gaap_AllowanceForDoubtfulAccountsReceivableRecoveries  
Write off of uncollectible accounts (229,000)us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs (315,000)us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs (331,000)us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs  
Ending balance 250,000us-gaap_AllowanceForDoubtfulAccountsReceivable 221,000us-gaap_AllowanceForDoubtfulAccountsReceivable 241,000us-gaap_AllowanceForDoubtfulAccountsReceivable  
Cash and Cash Equivalents [Abstract]        
Maximum maturity period of temporary cash investments consider as cash equivalents 3 months      
Customer accounts receivable - water [Member]        
Summary of changes in entity's accounts receivable [Abstract]        
Gross accounts receivable 4,020,000us-gaap_AccountsReceivableGrossCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= us-gaap_TradeAccountsReceivableMember		 3,902,000us-gaap_AccountsReceivableGrossCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= us-gaap_TradeAccountsReceivableMember		 3,988,000us-gaap_AccountsReceivableGrossCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= us-gaap_TradeAccountsReceivableMember		  
Other [Member]        
Summary of changes in entity's accounts receivable [Abstract]        
Gross accounts receivable 1,295,000us-gaap_AccountsReceivableGrossCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= artna_OtherAccountsReceivableMember		 1,434,000us-gaap_AccountsReceivableGrossCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= artna_OtherAccountsReceivableMember		 1,981,000us-gaap_AccountsReceivableGrossCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= artna_OtherAccountsReceivableMember		  
7-Year Rate [Member]        
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  
10-Year Rate [Member]        
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 10 years 10 years  
Mountain Hill [Member]        
Summary of other deferred assets net of amortization [Abstract]        
Other 300,000us-gaap_OtherDeferredCostsNet
/ us-gaap_BusinessAcquisitionAxis
= artna_MountainHillMember		      
Minimum [Member]        
Other Deferred Assets [Abstract]        
Amortization period of debt issuance costs 10 years      
Maximum [Member]        
Other Deferred Assets [Abstract]        
Amortization period of debt issuance costs 30 years      
Maryland [Member]        
Regulatory Assets [Abstract]        
Amortization period of regulatory rate proceedings and applications 5 years      
Delaware [Member]        
Regulatory Assets [Abstract]        
Amortization period of regulatory rate proceedings and applications 2 years      
Postretirement benefit obligation [Member]        
Summary of regulatory assets net of amortization, comprise [Abstract]        
Regulatory assets, net 384,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= us-gaap_PostretirementBenefitCostsMember		 438,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= us-gaap_PostretirementBenefitCostsMember		    
Deferred income taxes [Member]        
Summary of regulatory assets net of amortization, comprise [Abstract]        
Regulatory assets, net 461,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_DeferredIncomeTaxesRecoverableInFutureRatesMember		 476,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_DeferredIncomeTaxesRecoverableInFutureRatesMember		    
Goodwill [Member]        
Summary of regulatory assets net of amortization, comprise [Abstract]        
Regulatory assets, net 325,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_GoodwillRTNMember		 333,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_GoodwillRTNMember		    
Deferred acquisition and franchise costs [Member]        
Summary of regulatory assets net of amortization, comprise [Abstract]        
Regulatory assets, net 756,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_DeferredAcquisitionAndFranchiseCostsMember		 792,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_DeferredAcquisitionAndFranchiseCostsMember		    
Expense of rate and regulatory proceedings [Member]        
Summary of regulatory assets net of amortization, comprise [Abstract]        
Regulatory assets, net $ 635,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_ExpenseOfRateAndRegulatoryProceedingsMember		 $ 265,000us-gaap_RegulatoryAssets
/ us-gaap_RegulatoryAssetAxis
= artna_ExpenseOfRateAndRegulatoryProceedingsMember