| Cover Page | Jan. 27, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Entity Registrant Name | ARROW FINANCIAL CORPORATION |
| Entity Incorporation, State or Country Code | NY |
| Entity File Number | 0-12507 |
| Entity Tax Identification Number | 22-2448962 |
| Entity Address, Address Line One | 250 Glen Street |
| Entity Address, City or Town | Glens Falls |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 12801 |
| City Area Code | 518 |
| Local Phone Number | 745-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, Par Value $1.00 per share |
| Trading Symbol | AROW |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000717538 |
| Amendment Flag | false |
| Document Period End Date | Jan. 27, 2021 |
