ACQUISITIONS (Details) (USD $)	3 Months Ended		6 Months Ended				6 Months Ended			6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jan. 19, 2012	Apr. 08, 2011	Jun. 30, 2012 Wilber Corporation [Member]	Apr. 08, 2011 Wilber Corporation [Member]	Nov. 30, 2011 Combined CAI Benefits and Wilber Corporation Acquisitions [Member]	Jun. 30, 2012 Combined HSBC and First Niagara Branch Agreements [Member]	Jan. 19, 2012 HSBC Branch Agreement [Member]	Jan. 19, 2012 First Niagara Branch Agreement [Member]
Business Acquisition [Line Items]
Number of new branch locations included in acquisition or purchase agreement					19			22			16	3
Loans to be Acquired											$ 107,000,000	$ 72,000,000
Deposits to be Acquired											697,000,000	138,000,000
Blended Deposit Premium											3.40%	3.20%
Amount of borrowings repaid			430,000,000
Public stock offering:
Amount raised through issuance			61,017,000	1,852,000						57,500,000
Number of shares issued (in shares)			2,130,000
Net proceeds from offering			54,917,000
Business Acquisition, Description of Acquired Entity			certain assets and liabilities of CAI Benefits, Inc. ("CAI"), a provider of actuarial, consulting and retirement plan administration services, with offices in New York City and Northern New Jersey
Assets acquired									1,400,000
Liabilities acquired									200,000
Cost of acquisition								103,000,000
Cash portion of purchase price								20,400,000
Issuance of shares of common stock (in shares)							3,350,000
Loans						462,300,000
Investment securities						297,600,000
Deposits						771,600,000
Borrowings						19,700,000
Merger and acquisition integration related expenses	$ 200,000	$ 3,600,000	$ 400,000	$ 4,300,000