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IMPACT OF RECENT ACCOUNTING PRONOUNCEMENTS (Details) $ in Millions | Dec. 31, 2020 USD ($)
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IMPACT OF RECENT ACCOUNTING PRONOUNCEMENTS [Abstract] |
Increase in reserve for bad debt | $ 0.5

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- Definition Increase in reserve for bad debt. + References No definition available. + Details
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Namespace Prefix: | artna_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration