Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 27, 2020	Jun. 30, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	Arrow Financial Corporation
Entity Central Index Key	0000717538
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		15,014,587
Entity Well-known Seasoned Filer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 502,734,584