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ACQUISITIONS (Details) shares in Thousands, $ in Millions |  |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
May 12, 2017 USD ($) Branch Location shares | Feb. 03, 2017 USD ($) | Sep. 30, 2017 USD ($) | Jun. 30, 2017 USD ($) | Sep. 30, 2017 USD ($)
Business Acquisition [Line Items] |  |  |  |  |
Increase (decrease) in other assets as a result of reclassification and adjustment |  |  | $ 5.5 | $ (2.7) |
Increase (decrease) in other liabilities as a result of reclassification and adjustment |  |  | 6.6 | (2.4) |
Increase in investments as a result of updated information not available at the time of acquisition |  |  | 0.2 |  |
Decrease in loans as a result of an adjustment to the valuation of acquired impaired loans |  |  | (0.6) |  |
Increase in premises and equipment as a result of updated appraisal information not available at the time of acquisition |  |  | 3.6 |  |
Merchants Bancshares, Inc. [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Issuance of common shares (in shares) | shares | 4,680 |  |  |  |
Assets acquired | $ 1,990.0 |  |  |  |
Revenues earned |  |  | 16.8 |  | $ 25.8
Expenses incurred |  |  | 7.5 |  | 11.5
Increase (decrease) in goodwill as a result of fair value adjustment |  |  | (2.0) |  |
Merchants Bancshares, Inc. [Member] | VERMONT [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Number of branch locations added upon merger | Branch | 31 |  |  |  |
Merchants Bancshares, Inc. [Member] | MASSACHUSETTS [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Number of branch locations added upon merger | Location | 1 |  |  |  |
Northeast Retirement Services, Inc. [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Tangible assets, net |  | $ 36.1 |  |  |
Factor of straight-line rate of depreciation used in declining balance depreciation method |  | 150.00% |  |  |
Period of amortization |  | 10 years |  |  |
Deferred tax liability |  | $ 24.2 |  |  |
Revenues earned |  |  | 8.7 |  | 22.1
Expenses incurred |  |  | 5.8 |  | $ 15.1
Increase (decrease) in goodwill as a result of fair value adjustment |  |  | $ (0.1) | $ 0.3 |

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