FAIR VALUE OF ASSETS AND LIABILITIES - Carrying value and estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Carrying value
Financial Assets
Cash and cash equivalents	$ 41,292	$ 35,485
Securities available-for-sale	76,849	79,623
Federal Home Loan Bank stock	3,510	3,211
Loans held-for-sale	53
Loans receivable, net	764,665	763,184
Accrued interest receivable	2,431	2,424
Cash surrender value of life insurance	14,126	14,038
Financial Liabilities
Demand (non-interest-bearing)	201,215	218,420
Demand (interest-bearing)	132,527	127,854
Money market	182,438	182,476
Savings and other	141,085	135,435
Certificates of deposit	115,151	117,585
Deposits	772,416	781,770
Repurchase agreements	2,350	5,535
FHLBB advances	52,745	37,188
Subordinated debt	9,794	9,788
Note payable	335	344
Capital lease liability	417	418
Accrued interest payable	238	89
Estimated fair value
Financial Assets
Cash and cash equivalents	41,292	35,485
Securities available-for-sale	76,849	79,623
Federal Home Loan Bank stock	3,510	3,211
Loans held-for-sale	53
Loans receivable, net	777,371	774,442
Accrued interest receivable	2,431	2,424
Cash surrender value of life insurance	14,126	14,038
Financial Liabilities
Demand (non-interest-bearing)	201,215	218,420
Demand (interest-bearing)	132,527	127,854
Money market	182,438	182,476
Savings and other	141,085	135,435
Certificates of deposit	116,305	118,610
Deposits	773,570	782,795
Repurchase agreements	2,350	5,535
FHLBB advances	53,857	38,440
Subordinated debt	10,391	10,378
Note payable	370	377
Capital lease liability	829	841
Accrued interest payable	238	89
Fair Value Measurements Using - Level 1
Financial Assets
Cash and cash equivalents	41,292	35,485
Securities available-for-sale	994	1,040
Federal Home Loan Bank stock
Loans held-for-sale
Loans receivable, net
Accrued interest receivable
Cash surrender value of life insurance	14,126	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	75,855	78,583
Federal Home Loan Bank stock		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	3,510
Loans held-for-sale	53
Loans receivable, net	777,371	774,442
Accrued interest receivable	2,431	2,424
Cash surrender value of life insurance
Financial Liabilities
Demand (non-interest-bearing)	201,215	218,420
Demand (interest-bearing)	132,527	127,854
Money market	182,438	182,476
Savings and other	141,085	135,435
Certificates of deposit	116,305	118,610
Deposits	773,570	782,795
Repurchase agreements	2,350	5,535
FHLBB advances	53,857	38,440
Subordinated debt	10,391	10,378
Note payable	370	377
Capital lease liability	829	841
Accrued interest payable	$ 238	$ 89