Parent Only Financial Information Parent Only Statement of Cash Flows (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cash Flows from Operating Activities:
Net Income	$ 23,360,000		$ 21,795,000		$ 22,179,000
Gains on the Sale of Securities Available-for-Sale	137,000		527,000		949,000
Stock-Based Compensation Expense	360,000		372,000		424,000
Stock-Based Compensation Expense	360,000		372,000		424,000
Net Cash Provided By Operating Activities	30,641,000		36,673,000		32,460,000
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	49,928,000		16,295,000		58,718,000
Purchases of Securities Available-for-Sale	(113,953,000)		(136,416,000)		(197,029,000)
Net Cash Used In Investing Activities	(67,693,000)		(149,015,000)		(65,645,000)
Cash Flows from Financing Activities:
Stock Options Exercised	1,454,000		1,254,000		2,105,000
Shares Issued Under the Employee Stock Purchase Plan	488,000		477,000		484,000
Shares Issued for Dividend Reinvestment Plans			(1,280,000)		(1,822,000)
Tax Benefit from Exercise of Stock Options	25,000		23,000		68,000
Purchases of Treasury Stock	2,455,000		1,709,000		4,877,000
Cash Dividends Paid	(12,407,000)	[1]	(12,109,000)	[1]	(11,815,000)	[1]
Net Cash Provided By Financing Activities	33,367,000		113,490,000		38,281,000
Net Increase (Decrease) in Cash and Cash Equivalents	(3,685,000)		1,148,000		5,096,000
Cash and Cash Equivalents at Beginning of Year	49,980,000		48,832,000		43,736,000
Cash and Cash Equivalents at End of Year	46,295,000		49,980,000		48,832,000
Interest on Deposits and Borrowings	5,932,000		8,067,000		12,520,000
Shares Issued for Acquisition of Subsidiary	91,000		233,000		233,000
Arrow Financial Corporation [Member]
Cash Flows from Operating Activities:
Net Income	23,360,000		21,795,000		22,179,000
Undistributed Net Income of Subsidiaries	(10,344,000)		(9,155,000)		(9,666,000)
Gains on the Sale of Securities Available-for-Sale	0		0		(63,000)
Stock-Based Compensation Expense	197,000		198,000		175,000
Stock-Based Compensation Expense	360,000		372,000		424,000
Changes in Other Assets and Other Liabilities	(1,014,000)		(990,000)		(1,640,000)
Net Cash Provided By Operating Activities	12,559,000		12,220,000		11,409,000
Cash Flows from Investing Activities:
Proceeds from the Sale of Securities Available-for-Sale	45,000		45,000		681,000
Purchases of Securities Available-for-Sale	(45,000)		(45,000)		(359,000)
Net Cash Used In Investing Activities	0		0		322,000
Cash Flows from Financing Activities:
Stock Options Exercised	1,942,000		1,254,000		2,105,000
Shares Issued Under the Employee Stock Purchase Plan	0		477,000		484,000
Shares Issued for Dividend Reinvestment Plans	0		1,280,000		1,822,000
Tax Benefit from Exercise of Stock Options	25,000		23,000		68,000
Purchases of Treasury Stock	(2,455,000)		(1,709,000)		(4,877,000)
Cash Dividends Paid	(12,407,000)		(12,109,000)		(11,815,000)
Net Cash Provided By Financing Activities	(12,895,000)		(10,784,000)		(12,213,000)
Net Increase (Decrease) in Cash and Cash Equivalents	(336,000)		1,436,000		(482,000)
Cash and Cash Equivalents at Beginning of Year	3,349,000		1,913,000		2,395,000
Cash and Cash Equivalents at End of Year	3,013,000		3,349,000		1,913,000
Interest on Deposits and Borrowings	620,000		640,000		692,000
Shares Issued for Acquisition of Subsidiary	$ 91,000		$ 233,000		$ 233,000

[1] Cash dividends paid per share have been adjusted for the September 2014 2% stock dividend.