FAIR VALUE OF ASSETS AND LIABILITIES - Carrying value and estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Carrying value
Financial Assets
Cash and cash equivalents	$ 49,403	$ 35,485
Securities available-for-sale	85,508	79,623
Federal Home Loan Bank stock	3,038	3,211
Loans held-for-sale	561
Loans receivable, net	784,136	763,184
Accrued interest receivable	2,520	2,424
Cash surrender value of life insurance	14,297	14,038
Financial Liabilities
Demand (non-interest-bearing)	225,496	218,420
Demand (interest-bearing)	139,521	127,854
Money market	196,745	182,476
Savings and other	152,570	135,435
Certificates of deposit	117,657	117,585
Deposits	831,989	781,770
Repurchase agreements	4,529	5,535
FHLBB advances	27,364	37,188
Subordinated debt	9,805	9,788
Note payable	321	344
Capital lease liability	1,859	418
Accrued interest payable	246	89
Estimated fair value
Financial Assets
Cash and cash equivalents	49,403	35,485
Securities available-for-sale	85,508	79,623
Federal Home Loan Bank stock	3,038	3,211
Loans held-for-sale	561
Loans receivable, net	798,367	774,442
Accrued interest receivable	2,520	2,424
Cash surrender value of life insurance	14,297	14,038
Financial Liabilities
Demand (non-interest-bearing)	225,496	218,420
Demand (interest-bearing)	139,521	127,854
Money market	196,745	182,476
Savings and other	152,570	135,435
Certificates of deposit	118,642	118,610
Deposits	833,439	782,795
Repurchase agreements	4,529	5,535
FHLBB advances	28,212	38,440
Subordinated debt	10,394	10,378
Note payable	351	377
Capital lease liability	2,249	841
Accrued interest payable	246	89
Fair Value Measurements Using - Level 1
Financial Assets
Cash and cash equivalents	49,403	35,485
Securities available-for-sale	1,028	1,040
Federal Home Loan Bank stock
Loans held-for-sale
Loans receivable, net
Accrued interest receivable
Cash surrender value of life insurance	14,297	14,038
Financial Liabilities
Demand (non-interest-bearing)
Demand (interest-bearing)
Money market
Savings and other
Certificates of deposit
Deposits
Repurchase agreements
FHLBB advances
Subordinated debt
Note payable
Capital lease liability
Accrued interest payable
Fair Value Measurements Using - Level 2
Financial Assets
Cash and cash equivalents
Securities available-for-sale	84,480	78,583
Federal Home Loan Bank stock	3,038	3,211
Loans held-for-sale
Loans receivable, net
Accrued interest receivable
Cash surrender value of life insurance
Financial Liabilities
Demand (non-interest-bearing)
Demand (interest-bearing)
Money market
Savings and other
Certificates of deposit
Deposits
Repurchase agreements
FHLBB advances
Subordinated debt
Note payable
Capital lease liability
Accrued interest payable
Fair Value Measurements Using - Level 3
Financial Assets
Cash and cash equivalents
Securities available-for-sale
Federal Home Loan Bank stock
Loans held-for-sale	561
Loans receivable, net	798,367	774,442
Accrued interest receivable	2,520	2,424
Cash surrender value of life insurance
Financial Liabilities
Demand (non-interest-bearing)	225,496	218,420
Demand (interest-bearing)	139,521	127,854
Money market	196,745	182,476
Savings and other	152,570	135,435
Certificates of deposit	119,642	118,610
Deposits	833,439	782,795
Repurchase agreements	4,529	5,535
FHLBB advances	28,212	38,440
Subordinated debt	10,394	10,378
Note payable	351	377
Capital lease liability	2,249	841
Accrued interest payable	$ 246	$ 89