Junior Subordinated Debt (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 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 [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	Aug. 01, 1999
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	Aug. 01, 2029
NBT Statutory Trust I VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust I [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	Nov. 01, 2005
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	Dec. 01, 2035
NBT Statutory Trust II VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust II [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	Feb. 01, 2006
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	Mar. 01, 2036
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	Dec. 01, 2003
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	Jan. 01, 2034
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	Sep. 01, 2006
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	Sep. 01, 2036