Parent Only Financial Information Parent Only Income Statement (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Interest and Dividends on Investments	$ 66,861	$ 64,138	$ 69,379
Other Operating Income	1,238	1,024	1,170
Net Gains on Securities Transactions	110	540	865
Interest Expense	5,767	7,922	11,957
Salaries and Employee Benefits	30,941	31,182	31,703
Other Operating Expense	12,980	12,656	11,640
Income Tax Benefit	(10,174)	(9,079)	(9,661)
Net Income	23,360	21,795	22,179
Arrow Financial Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from Bank Subsidiaries	13,300	12,900	12,700
Interest and Dividends on Investments	116	116	123
Other Operating Income	578	549	776
Net Gains on Securities Transactions	0	0	63
Total Income	13,994	13,565	13,662
Interest Expense	620	640	692
Salaries and Employee Benefits	77	59	75
Other Operating Expense	754	860	957
Total Expense	1,451	1,559	1,724
Income Before Income Tax Benefit and Equity in Undistributed Net Income of Subsidiaries	12,543	12,006	11,938
Income Tax Benefit	(473)	(634)	(575)
Equity in Undistributed Net Income of Subsidiaries	10,344	9,155	9,666
Net Income	$ 23,360	$ 21,795	$ 22,179