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ACQUISITIONS (Details) shares in Thousands, $ in Thousands |  |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Oct. 24, 2016 USD ($) Location Branch | Dec. 04, 2015 USD ($) Branch shares | Mar. 31, 2016 USD ($) | Sep. 30, 2016 USD ($)
Business Acquisition [Line Items] |  |  |  |
Increase in goodwill as a result of fair value adjustment |  |  |  | $ 1,890
Merchants Bancshares, Inc. [Member] | Subsequent Event [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Purchase price of acquisition | $ 304,000 |  |  |
Deposits to be acquired | 1,500,000 |  |  |
Assets acquired | $ 1,900,000 |  |  |
Merchants Bancshares, Inc. [Member] | Subsequent Event [Member] | VERMONT [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Number of branch locations to be added upon merger | Branch | 31 |  |  |
Merchants Bancshares, Inc. [Member] | Subsequent Event [Member] | MASSACHUSETTS [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Number of branch locations to be added upon merger | Location | 1 |  |  |
Oneida Financial Corp [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Deposits to be acquired |  | $ 699,241 |  |
Issuance of common shares (in shares) | shares |  | 2,380 |  |
Number of new branch locations included in acquisition or purchase agreement | Branch |  | 12 |  |
Assets acquired |  | $ 769,000 |  |
Decrease in other assets as a result of fair value adjustment |  |  | $ (900) |
Increase in other liabilities as a result of fair value adjustment |  |  | 700 |
Increase in goodwill as a result of fair value adjustment |  |  | $ 1,600 |

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