Parent Only Financial Information Parent Only Balance Sheet (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Interest-Bearing Deposits at Banks	$ 11,214	$ 12,705
Available-for-sale Securities	366,139	457,606
Held-to-Maturity Securities	302,024	299,261
Other Assets	46,297	43,235
Total Assets	2,217,420	2,163,698
LIABILITIES
Junior Subordinated Obligations Issued to Unconsolidated Subsidiary Trusts	20,000	20,000
Other Liabilities	23,125	24,437
Total Liabilities	2,016,494	1,971,544
Equity [Abstract]
Stockholders' Equity Attributable to Parent	200,926	192,154	175,825	166,385
Total Liabilities and Stockholders' Equity	2,217,420	2,163,698
Arrow Financial Corporation [Member]
ASSETS
Interest-Bearing Deposits at Banks	3,013	3,349
Available-for-sale Securities	1,254	1,166
Held-to-Maturity Securities	1,000	1,000
Equity Method Investments	214,813	206,680
Other Assets	6,538	5,807
Total Assets	226,618	218,002
LIABILITIES
Junior Subordinated Obligations Issued to Unconsolidated Subsidiary Trusts	20,000	20,000
Other Liabilities	5,692	5,848
Total Liabilities	25,692	25,848
Equity [Abstract]
Stockholders' Equity Attributable to Parent	200,926	192,154
Total Liabilities and Stockholders' Equity	$ 226,618	$ 218,002