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Leases - Narrative (Details)	12 Months Ended
Leases - Narrative (Details)	Dec. 31, 2019 branch_office
Leases [Abstract]
Number of branch offices	5

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- Definition

Number of Leased Branch Offices

+ References

No definition available.

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Namespace Prefix:	arow_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_LeasesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration