Parent Only Financial Information Parent Only Balance Sheet (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
ASSETS
Interest-Bearing Deposits at Banks	$ 11,756	$ 14,138
Available-for-sale Securities	478,698	556,538
Held-to-Maturity Securities	239,803	150,688
Other Assets	30,716	32,567
Total Assets	2,022,796	1,962,684
LIABILITIES
Junior Subordinated Obligations Issued to Unconsolidated Subsidiary Trusts	20,000	20,000
Other Liabilities	23,554	22,813
Total Liabilities	1,846,971	1,796,299
Equity [Abstract]
Stockholders' Equity Attributable to Parent	175,825	166,385	152,259	140,818
Total Liabilities and Stockholders' Equity	2,022,796	1,962,684
Arrow Financial Corporation [Member]
ASSETS
Interest-Bearing Deposits at Banks	1,913	2,395
Available-for-sale Securities	1,148	1,433
Held-to-Maturity Securities	1,000	1,000
Equity Method Investments	192,985	184,515
Other Assets	5,339	3,915
Total Assets	202,385	193,258
LIABILITIES
Junior Subordinated Obligations Issued to Unconsolidated Subsidiary Trusts	20,000	20,000
Other Liabilities	6,560	6,873
Total Liabilities	26,560	26,873
Equity [Abstract]
Stockholders' Equity Attributable to Parent	175,825	166,385
Total Liabilities and Stockholders' Equity	$ 202,385	$ 193,258