Trust Preferred Debentures (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Limited Guarantee Trust Preferred Debentures [Abstract]
Number of statutory business trusts included in the Trusts	3
CNBF Capital Trust I VIE Entity Not Primary Beneficiary [Member] | CNBF Capital Trust I Debenture [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
Issuance Date	June 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	August 2029
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 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	December 2035
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 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	March 2036