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Federal Reserve Bank Requirement	12 Months Ended
Federal Reserve Bank Requirement	Dec. 31, 2011
Federal Reserve Bank Requirement [Abstract]
Federal Reserve Bank Requirement	(4) Federal Reserve Bank Requirement The Company is required to maintain reserve balances with the Federal Reserve Bank. The required average total reserve for NBT Bank for the 14-day maintenance period ending December 31, 2011 was $33.4 million.