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Risks and Uncertainties - Narrative (Details) | 12 Months Ended
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Dec. 31, 2020 bank subsidiaryBusinessTrust
Risks and Uncertainties [Abstract] |
Number of banks | bank | 2
Number of business subsidiary trusts | subsidiaryBusinessTrust | 2

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- Definition Number of Banks + References No definition available. + Details
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- Definition Number of Business Subsidiary Trusts + References No definition available. + Details
Name: | arow_NumberofBusinessSubsidiaryTrusts
Namespace Prefix: | arow_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_RisksAndUncertaintiesAbstract
Namespace Prefix: | us-gaap_
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