Regulatory Matters (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Arrow Financial Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk Weighted Assets) - Actual Amount	$ 225,766	$ 212,360
Total Capital (to Risk Weighted Assets) - Actual Ratio	15.50%	15.80%
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	116,524	107,524
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	8.00%	8.00%
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Amount	145,655	134,405
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	10.00%	10.00%
Tier I Capital (to Risk Weighted Assets) - Actual Amount	210,136	197,906
Tier I Capital (to Risk Weighted Assets) - Actual Ratio	14.50%	14.70%
Tier I Capital (to Risk Weighted Assets) - Minimum Acounts For Capital Adequacy Purposes Amount	57,969	53,852
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	4.00%	4.00%
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	86,953	80,778
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	6.00%	6.00%
Tier I Capital (to Average Assets) - Actual Amount	210,136	197,906
Tier I Capital (to Average Assets) - Actual Ratio	9.40%	9.20%
Tier I Capital (to Average Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	89,420	86,046
Tier I Capital (to Average Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	4.00%	4.00%
Tier I Capital (to Average Assets) - Minimum Amounts To Be Well-Capitalized Amount	89,420	86,046
Tier I Capital (to Average Assets) - Minimum Amounts To Be Well-Capitalized Ratio	4.00%	4.00%
Glens Falls National [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk Weighted Assets) - Actual Amount	183,446	172,720
Total Capital (to Risk Weighted Assets) - Actual Ratio	15.50%	15.40%
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	94,682	89,725
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	8.00%	8.00%
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Amount	118,352	112,156
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	10.00%	10.00%
Tier I Capital (to Risk Weighted Assets) - Actual Amount	170,497	160,849
Tier I Capital (to Risk Weighted Assets) - Actual Ratio	14.40%	14.40%
Tier I Capital (to Risk Weighted Assets) - Minimum Acounts For Capital Adequacy Purposes Amount	47,360	44,680
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	4.00%	4.00%
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	71,040	67,020
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	6.00%	6.00%
Tier I Capital (to Average Assets) - Actual Amount	170,497	160,849
Tier I Capital (to Average Assets) - Actual Ratio	9.10%	8.80%
Tier I Capital (to Average Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	74,944	73,113
Tier I Capital (to Average Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	4.00%	4.00%
Tier I Capital (to Average Assets) - Minimum Amounts To Be Well-Capitalized Amount	93,680	91,391
Tier I Capital (to Average Assets) - Minimum Amounts To Be Well-Capitalized Ratio	5.00%	5.00%
Saratoga National [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk Weighted Assets) - Actual Amount	35,217	33,396
Total Capital (to Risk Weighted Assets) - Actual Ratio	13.30%	14.80%
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	21,183	18,052
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	8.00%	8.00%
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Amount	26,479	22,565
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	10.00%	10.00%
Tier I Capital (to Risk Weighted Assets) - Actual Amount	32,596	30,833
Tier I Capital (to Risk Weighted Assets) - Actual Ratio	12.30%	13.70%
Tier I Capital (to Risk Weighted Assets) - Minimum Acounts For Capital Adequacy Purposes Amount	10,600	9,002
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	4.00%	4.00%
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	15,900	13,504
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	6.00%	6.00%
Tier I Capital (to Average Assets) - Actual Amount	32,596	30,833
Tier I Capital (to Average Assets) - Actual Ratio	9.40%	9.70%
Tier I Capital (to Average Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	13,871	12,715
Tier I Capital (to Average Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	4.00%	4.00%
Tier I Capital (to Average Assets) - Minimum Amounts To Be Well-Capitalized Amount	$ 17,338	$ 15,893
Tier I Capital (to Average Assets) - Minimum Amounts To Be Well-Capitalized Ratio	5.00%	5.00%