Carrying value and estimated fair values of financial instruments - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financial Assets
Cash and cash equivalents		$ 26,885
Interest bearing time deposits with financial institutions		750
Securities available-for-sale		91,801
CRA mutual fund		882
Federal Home Loan Bank of Boston stock		3,242
Loans held-for-sale		332
Loans receivable, net		927,413
Accrued interest receivable		3,415
Cash surrender value of life insurance policies		20,580
Financial Liabilities
Demand (non-interest-bearing)		237,852
Demand (interest-bearing)		153,314
Money market		239,504
Savings and other		161,112
Certificates of deposit		127,724
Deposits		919,506
Repurchase agreements		8,530
FHLBB advances		50,887
Subordinated debt		9,859
Note payable		246
Finance lease liability		1,718
Accrued interest payable		78
Reported Value Measurement [Member]
Financial Assets
Cash and cash equivalents	$ 95,341
Interest bearing time deposits with financial institutions	750
Securities available-for-sale	95,720
CRA mutual fund	916
Federal Home Loan Bank of Boston stock	3,158
Loans held-for-sale	2,761
Loans receivable, net	1,031,593
Accrued interest receivable	6,055
Cash surrender value of life insurance policies	17,572
Financial Liabilities
Demand (non-interest-bearing)	313,742
Demand (interest-bearing)	201,760
Money market	270,097
Savings and other	181,691
Certificates of deposit	127,851
Deposits	1,095,141
Repurchase agreements	10,885
FHLBB advances	43,880
Subordinated debt	9,877
Note payable	218
Finance lease liability	1,685
Accrued interest payable	210
Derivative financial instruments	3
Estimate of Fair Value Measurement [Member]
Financial Assets
Cash and cash equivalents	95,341	26,885
Interest bearing time deposits with financial institutions	750	750
Securities available-for-sale	95,720	91,801
CRA mutual fund	916	882
Federal Home Loan Bank of Boston stock	3,158	3,242
Loans held-for-sale	2,802	334
Loans receivable, net	1,058,564	933,287
Accrued interest receivable	6,055	3,415
Cash surrender value of life insurance policies	17,572	20,580
Financial Liabilities
Demand (non-interest-bearing)	313,742	237,852
Demand (interest-bearing)	201,760	153,314
Money market	270,097	239,504
Savings and other	181,691	161,112
Certificates of deposit	129,311	128,629
Deposits	1,096,601	920,411
Repurchase agreements	10,885	8,530
FHLBB advances	44,099	51,028
Subordinated debt	9,965	10,113
Note payable	222	251
Finance lease liability	1,868	1,967
Accrued interest payable	210	78
Derivative financial instruments	3
Fair Value, Inputs, Level 1 [Member]
Financial Assets
Cash and cash equivalents	95,341	26,885
Interest bearing time deposits with financial institutions	750	750
Securities available-for-sale
CRA mutual fund	916	882
Federal Home Loan Bank of Boston stock	3,158	3,242
Loans held-for-sale
Loans receivable, net
Accrued interest receivable	6,055	3,415
Cash surrender value of life insurance policies	17,572	20,580
Financial Liabilities
Demand (non-interest-bearing)
Demand (interest-bearing)
Money market
Savings and other
Certificates of deposit
Deposits
Repurchase agreements
FHLBB advances
Subordinated debt	9,965	10,113
Note payable
Finance lease liability
Accrued interest payable	210	78
Derivative financial instruments
Fair Value, Inputs, Level 2 [Member]
Financial Assets
Cash and cash equivalents
Interest bearing time deposits with financial institutions
Securities available-for-sale	95,720	91,801
CRA mutual fund
Federal Home Loan Bank of Boston stock
Loans held-for-sale
Loans receivable, net
Accrued interest receivable
Cash surrender value of life insurance policies
Financial Liabilities
Demand (non-interest-bearing)	313,742	237,852
Demand (interest-bearing)	201,760	153,314
Money market	270,097	239,504
Savings and other	181,691	161,112
Certificates of deposit	129,311	128,629
Deposits	1,096,601	920,411
Repurchase agreements	10,885	8,530
FHLBB advances	44,099	51,028
Subordinated debt
Note payable	222	251
Finance lease liability
Accrued interest payable
Derivative financial instruments	3
Fair Value, Inputs, Level 3 [Member]
Financial Assets
Cash and cash equivalents
Interest bearing time deposits with financial institutions
Securities available-for-sale
CRA mutual fund
Federal Home Loan Bank of Boston stock
Loans held-for-sale	2,802	334
Loans receivable, net	1,058,564	933,287
Accrued interest receivable
Cash surrender value of life insurance policies
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
Finance lease liability	1,868	1,967
Accrued interest payable
Derivative financial instruments