ACQUISITIONS, Intangible Asset, Goodwill and Acquisition-related Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Summary of loans acquired [Abstract]
Merger and acquisition integration-related expenses	$ 580	$ 2	$ 25,192	$ 342
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
Benefits Advisory Service, Inc [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life			8 years
Benefits Advisory Service, Inc [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life			8 years
Dryfoos Insurance Agency, Inc [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life			8 years
Dryfoos Insurance Agency, Inc [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