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ACQUISITIONS, Intangible Asset, Goodwill and Acquisition-related Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of loans acquired [Abstract]
Merger and acquisition integration-related expenses	$ 25,986	$ 1,706	$ 7,037
Merchants Bancshares, Inc. [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Merchants Bancshares, Inc. [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Dryfoos [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Dryfoos [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
BAS [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
BAS [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
WJL Agencies Inc [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
WJL Agencies Inc [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Oneida Financial Corp [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Oneida Financial Corp [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years

X

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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