Parent Only Financial Information Parent Only Income Statement (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Interest and Dividends on Investments	$ 69,379	$ 76,791	$ 84,972
Other Operating Income	1,170	746	316
Net Gains on Securities Transactions	865	2,795	1,507
Interest Expense	11,957	18,679	23,695
Salaries and Employee Benefits	31,703	30,205	27,552
Other Operating Expense	11,640	11,044	11,035
Income Tax Benefit	(9,661)	(9,714)	(9,754)
Net Income	22,179	21,933	21,892
Arrow Financial Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from Bank Subsidiaries	12,700	14,450	12,400
Interest and Dividends on Investments	123	127	129
Other Operating Income	776	596	720
Net Gains on Securities Transactions	63	17	27
Total Income	13,662	15,190	13,276
Interest Expense	692	669	666
Salaries and Employee Benefits	75	92	109
Other Operating Expense	957	820	908
Total Expense	1,724	1,581	1,683
Income Before Income Tax Benefit and Equity in Undistributed Net Income of Subsidiaries	11,938	13,609	11,593
Income Tax Benefit	575	477	489
Equity in Undistributed Net Income of Subsidiaries	9,666	7,847	9,810
Net Income	$ 22,179	$ 21,933	$ 21,892