Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Maximum Subsidiary Dividend	$ 44,100
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk Weighted Assets) - Actual Amount	$ 278,163	$ 258,653
Total Capital (to Risk Weighted Assets) - Actual Ratio	15.00%	15.20%
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	$ 172,461	$ 146,343
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	9.30%	8.60%
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Amount	$ 185,442	$ 170,166
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	$ 259,378	$ 241,523
Tier I Capital (to Risk Weighted Assets) - Actual Ratio	14.00%	14.10%
Tier I Capital (to Risk Weighted Assets) - Minimum Acounts For Capital Adequacy Purposes Amount	$ 135,247	$ 113,053
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	7.30%	6.60%
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	$ 148,216	$ 137,034
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital	$ 259,378	$ 241,523
Tier One Leverage Capital to Average Assets	9.50%	9.50%
Tier One Leverage Capital Required for Capital Adequacy	$ 109,212	$ 101,694
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 136,515	$ 127,117
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Common Equity Tier 1 Capital Ratio	$ 239,326	$ 221,472
Common Equity Tier 1 Capital Ratio Percentage	12.90%	13.00%
Common Equity Tier 1 Capital Ratio Required for Capital Adequacy	$ 107,604	$ 86,885
Common Equity Tier 1 Capital Ratio For Capital Adequacy	5.80%	5.10%
Common Equity Tier 1 Leverage Capital Required to be Well Capitalized	$ 120,591	$ 110,736
Common Equity Tier 1 Capital Ratio to be Well Capitalized	6.50%	6.50%
Glens Falls National [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk Weighted Assets) - Actual Amount	$ 220,275	$ 205,573
Total Capital (to Risk Weighted Assets) - Actual Ratio	14.60%	15.00%
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	$ 140,312	$ 117,862
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	9.30%	8.60%
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Amount	$ 150,873	$ 137,049
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	$ 205,200	$ 191,679
Tier I Capital (to Risk Weighted Assets) - Actual Ratio	13.60%	14.00%
Tier I Capital (to Risk Weighted Assets) - Minimum Acounts For Capital Adequacy Purposes Amount	$ 110,144	$ 90,363
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	7.30%	6.60%
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	$ 120,706	$ 109,531
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital	$ 205,200	$ 191,679
Tier One Leverage Capital to Average Assets	9.10%	9.10%
Tier One Leverage Capital Required for Capital Adequacy	$ 90,198	$ 84,255
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 112,747	$ 105,318
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Common Equity Tier 1 Capital Ratio	$ 205,148	$ 191,628
Common Equity Tier 1 Capital Ratio Percentage	13.60%	13.90%
Common Equity Tier 1 Capital Ratio Required for Capital Adequacy	$ 87,490	$ 70,310
Common Equity Tier 1 Capital Ratio For Capital Adequacy	5.80%	5.10%
Common Equity Tier 1 Leverage Capital Required to be Well Capitalized	$ 98,049	$ 89,610
Common Equity Tier 1 Capital Ratio to be Well Capitalized	6.50%	6.50%
Saratoga National [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to Risk Weighted Assets) - Actual Amount	$ 48,822	$ 42,168
Total Capital (to Risk Weighted Assets) - Actual Ratio	14.00%	12.80%
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Amount	$ 32,432	$ 28,332
Total Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	9.30%	8.60%
Total Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Amount	$ 34,873	$ 32,944
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	$ 45,311	$ 39,050
Tier I Capital (to Risk Weighted Assets) - Actual Ratio	13.00%	11.90%
Tier I Capital (to Risk Weighted Assets) - Minimum Acounts For Capital Adequacy Purposes Amount	$ 25,444	$ 21,658
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts For Capital Adequacy Purposes Ratio	7.30%	6.60%
Tier I Capital (to Risk Weighted Assets) - Minimum Amounts To Be Well-Capitalized Ratio	$ 27,884	$ 26,252
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital	$ 45,311	$ 39,050
Tier One Leverage Capital to Average Assets	9.40%	8.90%
Tier One Leverage Capital Required for Capital Adequacy	$ 19,281	$ 17,551
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 24,102	$ 21,938
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Common Equity Tier 1 Capital Ratio	$ 45,311	$ 39,050
Common Equity Tier 1 Capital Ratio Percentage	13.00%	11.90%
Common Equity Tier 1 Capital Ratio Required for Capital Adequacy	$ 20,216	$ 16,736
Common Equity Tier 1 Capital Ratio For Capital Adequacy	5.80%	5.10%
Common Equity Tier 1 Leverage Capital Required to be Well Capitalized	$ 22,656	$ 21,330
Common Equity Tier 1 Capital Ratio to be Well Capitalized	6.50%	6.50%