Trust Preferred Debentures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Limited Guarantee Trust Preferred Debentures [Abstract]
Number of statutory business trusts included in the Trusts	5
CNBF Capital Trust I VIE Entity Not Primary Beneficiary [Member] | CNBF Capital Trust I Debenture [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	August-99
Trust Preferred Securities Outstanding	$ 18,000
Interest Rate	3-month LIBOR plus 2.75%
Trust Preferred Debt Owed To Trust	18,720
Final Maturity date	August-29
NBT Statutory Trust I VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust I Debenture [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	November-05
Trust Preferred Securities Outstanding	5,000
Interest Rate	3-month LIBOR plus 1.40%
Trust Preferred Debt Owed To Trust	5,155
Final Maturity date	December-35
NBT Statutory Trust II VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust II Debenture [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	February-06
Trust Preferred Securities Outstanding	50,000
Interest Rate	3-month LIBOR plus 1.40%
Trust Preferred Debt Owed To Trust	51,547
Final Maturity date	March-36
Alliance Financial Capital Trust I VIE Entity Not Primary Beneficiary [Member] | Alliance Financial Capital Trust I [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	December-03
Trust Preferred Securities Outstanding	10,000
Interest Rate	3-month LIBOR plus 2.85%
Trust Preferred Debt Owed To Trust	10,310
Final Maturity date	January-34
Alliance Financial Capital Trust II VIE Entity Not Primary Beneficiary [Member] | Alliance Financial Capital Trust II [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	September-06
Trust Preferred Securities Outstanding	15,000
Interest Rate	3-month LIBOR plus 1.65%
Trust Preferred Debt Owed To Trust	$ 15,464
Final Maturity date	September-36