FAIR VALUE MEASUREMENTS - Changes in Level 3 (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)
Interest Rate Lock Commitment
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 0
Acquisition of Lake Sunapee Bank, January 13, 2017	96,000
Goodwill adjustment Lake Sunapee Bank Merger	(75,000)
Realized (loss) recognized in non-interest income	(22,000)
Ending balance	(1,000)
Forward Commitments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	0
Acquisition of Lake Sunapee Bank, January 13, 2017	23,000
Goodwill adjustment Lake Sunapee Bank Merger	(167,000)
Realized (loss) recognized in non-interest income	(77,000)
Ending balance	$ (221,000)