Parent Only Financial Information Parent Only Statement of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows from Operating Activities:
Net Income	$ 22,179	$ 21,933	$ 21,892
Net Gains on the Sale of Securities Available-for-Sale	949	2,795	1,507
Shares Issued Under the Directors' Stock Plan	(175)	(175)	(149)
Stock-Based Compensation Expense	424	354	299
Net Cash Provided By Operating Activities	32,460	36,085	10,219
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	58,718	39,009	25,497
Purchases of Securities Available-for-Sale	(197,029)	(354,310)	(382,614)
Net Cash Used In Investing Activities	(65,645)	(44,796)	(93,749)
Cash Flows from Financing Activities:
Stock Options Exercised	2,105	1,413	798
Shares Issued Under the Employee Stock Purchase Plan	484	474	475
Shares Issued for Dividend Reinvestment Plans	1,822	1,796	1,715
Tax Benefit from Exercise of Stock Options	68	51	105
Purchases of Treasury Stock	(4,877)	(6,039)	(3,347)
Cash Dividends Paid	(11,815)	(11,448)	(10,997)
Net Cash Provided By Financing Activities	38,281	21,368	47,493
Net Increase (Decrease) in Cash and Cash Equivalents	5,096	12,657	(36,037)
Cash and Cash Equivalents at Beginning of Year	43,736	31,079	67,116
Cash and Cash Equivalents at End of Year	48,832	43,736	31,079
Interest on Deposits and Borrowings	12,520	19,490	23,995
Shares Issued for Acquisition of Subsidiary	233	5,261	682
Arrow Financial Corporation [Member]
Cash Flows from Operating Activities:
Net Income	22,179	21,933	21,892
Undistributed Net Income of Subsidiaries	(9,666)	(7,847)	(9,810)
Net Gains on the Sale of Securities Available-for-Sale	(63)	(17)	(27)
Shares Issued Under the Directors' Stock Plan	175	175	149
Stock-Based Compensation Expense	424	354	299
Changes in Other Assets and Other Liabilities	(1,640)	(165)	(1,253)
Net Cash Provided By Operating Activities	11,409	14,433	11,250
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	681	410	270
Purchases of Securities Available-for-Sale	(359)	(253)	(373)
Net Cash Used In Investing Activities	322	157	(103)
Cash Flows from Financing Activities:
Stock Options Exercised	2,105	1,413	798
Shares Issued Under the Employee Stock Purchase Plan	484	474	475
Shares Issued for Dividend Reinvestment Plans	1,822	1,796	1,715
Tax Benefit from Exercise of Stock Options	68	51	105
Purchases of Treasury Stock	(4,877)	(6,039)	(3,347)
Cash Dividends Paid	(11,815)	(11,448)	(10,997)
Net Cash Provided By Financing Activities	(12,213)	(13,753)	(11,251)
Net Increase (Decrease) in Cash and Cash Equivalents	(482)	837	(104)
Cash and Cash Equivalents at Beginning of Year	2,395	1,558	1,662
Cash and Cash Equivalents at End of Year	1,913	2,395	1,558
Interest on Deposits and Borrowings	692	669	666
Shares Issued for Acquisition of Subsidiary	$ 233	$ 5,261	$ 682