Trust Preferred Debentures (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2009	Dec. 31, 2010
Variable Interest Entity [Line Items]
Trust preferred debt owed to trust	$ 75,422,000		$ 75,422,000
Wholly owned Delaware statutory business trusts - variable interest entities	three wholly owned Delaware statutory business trusts
Common equity securities issued by Variable Interest Entity to NBT		33,401,000
Deferral period of payments of interest, description	Ten consecutive semi-annual periods with respect to each deferral period
Tier I risk based regulatory capital included from Trust preferred securities issued by subsidiary trusts	74,000,000
Minimum assets for bank holding companies to be subject to the same capital requirements as insured depository institutions	500,000,000
CNBF Capital Trust I VIE Entity Not Primary Beneficiary [Member] | CNBF Capital Trust I Debenture [Member]
Variable Interest Entity [Line Items]
Trust preferred debt owed to trust	18,720,000
Trust Preferred Securities Outstanding	18,000,000
Issuance Date	June 1999
Interest Rate	three-month LIBOR plus 275 basis points
Final Maturity Date	2029-08-31
Common equity securities issued by Variable Interest Entity to NBT	700,000
CNBF Trust I securities owned by bank	1,000,000
NBT Statutory Trust I VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust I Debenture [Member]
Variable Interest Entity [Line Items]
Trust preferred debt owed to trust	5,155,000
Trust Preferred Securities Outstanding	5,000,000
Issuance Date	November 2005
Interest Rate	three-month LIBOR plus 140 basis points
Final Maturity Date	2035-12-01
Common equity securities issued by Variable Interest Entity to NBT	200,000
Original issuance fixed interest rate (in hundredths)	6.30%
NBT Statutory Trust II VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust II Debenture [Member]
Variable Interest Entity [Line Items]
Trust preferred debt owed to trust	51,547,000
Trust Preferred Securities Outstanding	50,000,000
Issuance Date	February 2006
Interest Rate	(three-month LIBOR plus 140 basis points)
Final Maturity Date	2036-03-15
Common equity securities issued by Variable Interest Entity to NBT	$ 1,500,000
Original issuance fixed interest rate (in hundredths)	6.195%
Fixed rate to convert to a floating rate (in years)	5Y