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v3.19.1

Leases - Narrative (Details) | 12 Months Ended
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Dec. 31, 2018 branch_office
Leases [Abstract] |
Number of branch offices | 5

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- Definition Number of Branch Offices + References No definition available. + Details
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Namespace Prefix: | arow_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration